python-3.6.zip added from Github

README.cosmo contains the necessary links.

third_party/python/Lib/importlib/__init__.py

@@ -0,0 +1,173 @@
+"""A pure Python implementation of import."""
+__all__ = ['__import__', 'import_module', 'invalidate_caches', 'reload']
+
+# Bootstrap help #####################################################
+
+# Until bootstrapping is complete, DO NOT import any modules that attempt
+# to import importlib._bootstrap (directly or indirectly). Since this
+# partially initialised package would be present in sys.modules, those
+# modules would get an uninitialised copy of the source version, instead
+# of a fully initialised version (either the frozen one or the one
+# initialised below if the frozen one is not available).
+import _imp  # Just the builtin component, NOT the full Python module
+import sys
+
+try:
+    import _frozen_importlib as _bootstrap
+except ImportError:
+    from . import _bootstrap
+    _bootstrap._setup(sys, _imp)
+else:
+    # importlib._bootstrap is the built-in import, ensure we don't create
+    # a second copy of the module.
+    _bootstrap.__name__ = 'importlib._bootstrap'
+    _bootstrap.__package__ = 'importlib'
+    try:
+        _bootstrap.__file__ = __file__.replace('__init__.py', '_bootstrap.py')
+    except NameError:
+        # __file__ is not guaranteed to be defined, e.g. if this code gets
+        # frozen by a tool like cx_Freeze.
+        pass
+    sys.modules['importlib._bootstrap'] = _bootstrap
+
+try:
+    import _frozen_importlib_external as _bootstrap_external
+except ImportError:
+    from . import _bootstrap_external
+    _bootstrap_external._setup(_bootstrap)
+    _bootstrap._bootstrap_external = _bootstrap_external
+else:
+    _bootstrap_external.__name__ = 'importlib._bootstrap_external'
+    _bootstrap_external.__package__ = 'importlib'
+    try:
+        _bootstrap_external.__file__ = __file__.replace('__init__.py', '_bootstrap_external.py')
+    except NameError:
+        # __file__ is not guaranteed to be defined, e.g. if this code gets
+        # frozen by a tool like cx_Freeze.
+        pass
+    sys.modules['importlib._bootstrap_external'] = _bootstrap_external
+
+# To simplify imports in test code
+_w_long = _bootstrap_external._w_long
+_r_long = _bootstrap_external._r_long
+
+# Fully bootstrapped at this point, import whatever you like, circular
+# dependencies and startup overhead minimisation permitting :)
+
+import types
+import warnings
+
+
+# Public API #########################################################
+
+from ._bootstrap import __import__
+
+
+def invalidate_caches():
+    """Call the invalidate_caches() method on all meta path finders stored in
+    sys.meta_path (where implemented)."""
+    for finder in sys.meta_path:
+        if hasattr(finder, 'invalidate_caches'):
+            finder.invalidate_caches()
+
+
+def find_loader(name, path=None):
+    """Return the loader for the specified module.
+
+    This is a backward-compatible wrapper around find_spec().
+
+    This function is deprecated in favor of importlib.util.find_spec().
+
+    """
+    warnings.warn('Use importlib.util.find_spec() instead.',
+                  DeprecationWarning, stacklevel=2)
+    try:
+        loader = sys.modules[name].__loader__
+        if loader is None:
+            raise ValueError('{}.__loader__ is None'.format(name))
+        else:
+            return loader
+    except KeyError:
+        pass
+    except AttributeError:
+        raise ValueError('{}.__loader__ is not set'.format(name)) from None
+
+    spec = _bootstrap._find_spec(name, path)
+    # We won't worry about malformed specs (missing attributes).
+    if spec is None:
+        return None
+    if spec.loader is None:
+        if spec.submodule_search_locations is None:
+            raise ImportError('spec for {} missing loader'.format(name),
+                              name=name)
+        raise ImportError('namespace packages do not have loaders',
+                          name=name)
+    return spec.loader
+
+
+def import_module(name, package=None):
+    """Import a module.
+
+    The 'package' argument is required when performing a relative import. It
+    specifies the package to use as the anchor point from which to resolve the
+    relative import to an absolute import.
+
+    """
+    level = 0
+    if name.startswith('.'):
+        if not package:
+            msg = ("the 'package' argument is required to perform a relative "
+                   "import for {!r}")
+            raise TypeError(msg.format(name))
+        for character in name:
+            if character != '.':
+                break
+            level += 1
+    return _bootstrap._gcd_import(name[level:], package, level)
+
+
+_RELOADING = {}
+
+
+def reload(module):
+    """Reload the module and return it.
+
+    The module must have been successfully imported before.
+
+    """
+    if not module or not isinstance(module, types.ModuleType):
+        raise TypeError("reload() argument must be a module")
+    try:
+        name = module.__spec__.name
+    except AttributeError:
+        name = module.__name__
+
+    if sys.modules.get(name) is not module:
+        msg = "module {} not in sys.modules"
+        raise ImportError(msg.format(name), name=name)
+    if name in _RELOADING:
+        return _RELOADING[name]
+    _RELOADING[name] = module
+    try:
+        parent_name = name.rpartition('.')[0]
+        if parent_name:
+            try:
+                parent = sys.modules[parent_name]
+            except KeyError:
+                msg = "parent {!r} not in sys.modules"
+                raise ImportError(msg.format(parent_name),
+                                  name=parent_name) from None
+            else:
+                pkgpath = parent.__path__
+        else:
+            pkgpath = None
+        target = module
+        spec = module.__spec__ = _bootstrap._find_spec(name, pkgpath, target)
+        _bootstrap._exec(spec, module)
+        # The module may have replaced itself in sys.modules!
+        return sys.modules[name]
+    finally:
+        try:
+            del _RELOADING[name]
+        except KeyError:
+            pass

third_party/python/Lib/importlib/abc.py

@@ -0,0 +1,329 @@
+"""Abstract base classes related to import."""
+from . import _bootstrap
+from . import _bootstrap_external
+from . import machinery
+try:
+    import _frozen_importlib
+except ImportError as exc:
+    if exc.name != '_frozen_importlib':
+        raise
+    _frozen_importlib = None
+try:
+    import _frozen_importlib_external
+except ImportError as exc:
+    _frozen_importlib_external = _bootstrap_external
+import abc
+
+
+def _register(abstract_cls, *classes):
+    for cls in classes:
+        abstract_cls.register(cls)
+        if _frozen_importlib is not None:
+            try:
+                frozen_cls = getattr(_frozen_importlib, cls.__name__)
+            except AttributeError:
+                frozen_cls = getattr(_frozen_importlib_external, cls.__name__)
+            abstract_cls.register(frozen_cls)
+
+
+class Finder(metaclass=abc.ABCMeta):
+
+    """Legacy abstract base class for import finders.
+
+    It may be subclassed for compatibility with legacy third party
+    reimplementations of the import system.  Otherwise, finder
+    implementations should derive from the more specific MetaPathFinder
+    or PathEntryFinder ABCs.
+    """
+
+    @abc.abstractmethod
+    def find_module(self, fullname, path=None):
+        """An abstract method that should find a module.
+        The fullname is a str and the optional path is a str or None.
+        Returns a Loader object or None.
+        """
+
+
+class MetaPathFinder(Finder):
+
+    """Abstract base class for import finders on sys.meta_path."""
+
+    # We don't define find_spec() here since that would break
+    # hasattr checks we do to support backward compatibility.
+
+    def find_module(self, fullname, path):
+        """Return a loader for the module.
+
+        If no module is found, return None.  The fullname is a str and
+        the path is a list of strings or None.
+
+        This method is deprecated in favor of finder.find_spec(). If find_spec()
+        exists then backwards-compatible functionality is provided for this
+        method.
+
+        """
+        if not hasattr(self, 'find_spec'):
+            return None
+        found = self.find_spec(fullname, path)
+        return found.loader if found is not None else None
+
+    def invalidate_caches(self):
+        """An optional method for clearing the finder's cache, if any.
+        This method is used by importlib.invalidate_caches().
+        """
+
+_register(MetaPathFinder, machinery.BuiltinImporter, machinery.FrozenImporter,
+          machinery.PathFinder, machinery.WindowsRegistryFinder)
+
+
+class PathEntryFinder(Finder):
+
+    """Abstract base class for path entry finders used by PathFinder."""
+
+    # We don't define find_spec() here since that would break
+    # hasattr checks we do to support backward compatibility.
+
+    def find_loader(self, fullname):
+        """Return (loader, namespace portion) for the path entry.
+
+        The fullname is a str.  The namespace portion is a sequence of
+        path entries contributing to part of a namespace package. The
+        sequence may be empty.  If loader is not None, the portion will
+        be ignored.
+
+        The portion will be discarded if another path entry finder
+        locates the module as a normal module or package.
+
+        This method is deprecated in favor of finder.find_spec(). If find_spec()
+        is provided than backwards-compatible functionality is provided.
+
+        """
+        if not hasattr(self, 'find_spec'):
+            return None, []
+        found = self.find_spec(fullname)
+        if found is not None:
+            if not found.submodule_search_locations:
+                portions = []
+            else:
+                portions = found.submodule_search_locations
+            return found.loader, portions
+        else:
+            return None, []
+
+    find_module = _bootstrap_external._find_module_shim
+
+    def invalidate_caches(self):
+        """An optional method for clearing the finder's cache, if any.
+        This method is used by PathFinder.invalidate_caches().
+        """
+
+_register(PathEntryFinder, machinery.FileFinder)
+
+
+class Loader(metaclass=abc.ABCMeta):
+
+    """Abstract base class for import loaders."""
+
+    def create_module(self, spec):
+        """Return a module to initialize and into which to load.
+
+        This method should raise ImportError if anything prevents it
+        from creating a new module.  It may return None to indicate
+        that the spec should create the new module.
+        """
+        # By default, defer to default semantics for the new module.
+        return None
+
+    # We don't define exec_module() here since that would break
+    # hasattr checks we do to support backward compatibility.
+
+    def load_module(self, fullname):
+        """Return the loaded module.
+
+        The module must be added to sys.modules and have import-related
+        attributes set properly.  The fullname is a str.
+
+        ImportError is raised on failure.
+
+        This method is deprecated in favor of loader.exec_module(). If
+        exec_module() exists then it is used to provide a backwards-compatible
+        functionality for this method.
+
+        """
+        if not hasattr(self, 'exec_module'):
+            raise ImportError
+        return _bootstrap._load_module_shim(self, fullname)
+
+    def module_repr(self, module):
+        """Return a module's repr.
+
+        Used by the module type when the method does not raise
+        NotImplementedError.
+
+        This method is deprecated.
+
+        """
+        # The exception will cause ModuleType.__repr__ to ignore this method.
+        raise NotImplementedError
+
+
+class ResourceLoader(Loader):
+
+    """Abstract base class for loaders which can return data from their
+    back-end storage.
+
+    This ABC represents one of the optional protocols specified by PEP 302.
+
+    """
+
+    @abc.abstractmethod
+    def get_data(self, path):
+        """Abstract method which when implemented should return the bytes for
+        the specified path.  The path must be a str."""
+        raise IOError
+
+
+class InspectLoader(Loader):
+
+    """Abstract base class for loaders which support inspection about the
+    modules they can load.
+
+    This ABC represents one of the optional protocols specified by PEP 302.
+
+    """
+
+    def is_package(self, fullname):
+        """Optional method which when implemented should return whether the
+        module is a package.  The fullname is a str.  Returns a bool.
+
+        Raises ImportError if the module cannot be found.
+        """
+        raise ImportError
+
+    def get_code(self, fullname):
+        """Method which returns the code object for the module.
+
+        The fullname is a str.  Returns a types.CodeType if possible, else
+        returns None if a code object does not make sense
+        (e.g. built-in module). Raises ImportError if the module cannot be
+        found.
+        """
+        source = self.get_source(fullname)
+        if source is None:
+            return None
+        return self.source_to_code(source)
+
+    @abc.abstractmethod
+    def get_source(self, fullname):
+        """Abstract method which should return the source code for the
+        module.  The fullname is a str.  Returns a str.
+
+        Raises ImportError if the module cannot be found.
+        """
+        raise ImportError
+
+    @staticmethod
+    def source_to_code(data, path='<string>'):
+        """Compile 'data' into a code object.
+
+        The 'data' argument can be anything that compile() can handle. The'path'
+        argument should be where the data was retrieved (when applicable)."""
+        return compile(data, path, 'exec', dont_inherit=True)
+
+    exec_module = _bootstrap_external._LoaderBasics.exec_module
+    load_module = _bootstrap_external._LoaderBasics.load_module
+
+_register(InspectLoader, machinery.BuiltinImporter, machinery.FrozenImporter)
+
+
+class ExecutionLoader(InspectLoader):
+
+    """Abstract base class for loaders that wish to support the execution of
+    modules as scripts.
+
+    This ABC represents one of the optional protocols specified in PEP 302.
+
+    """
+
+    @abc.abstractmethod
+    def get_filename(self, fullname):
+        """Abstract method which should return the value that __file__ is to be
+        set to.
+
+        Raises ImportError if the module cannot be found.
+        """
+        raise ImportError
+
+    def get_code(self, fullname):
+        """Method to return the code object for fullname.
+
+        Should return None if not applicable (e.g. built-in module).
+        Raise ImportError if the module cannot be found.
+        """
+        source = self.get_source(fullname)
+        if source is None:
+            return None
+        try:
+            path = self.get_filename(fullname)
+        except ImportError:
+            return self.source_to_code(source)
+        else:
+            return self.source_to_code(source, path)
+
+_register(ExecutionLoader, machinery.ExtensionFileLoader)
+
+
+class FileLoader(_bootstrap_external.FileLoader, ResourceLoader, ExecutionLoader):
+
+    """Abstract base class partially implementing the ResourceLoader and
+    ExecutionLoader ABCs."""
+
+_register(FileLoader, machinery.SourceFileLoader,
+            machinery.SourcelessFileLoader)
+
+
+class SourceLoader(_bootstrap_external.SourceLoader, ResourceLoader, ExecutionLoader):
+
+    """Abstract base class for loading source code (and optionally any
+    corresponding bytecode).
+
+    To support loading from source code, the abstractmethods inherited from
+    ResourceLoader and ExecutionLoader need to be implemented. To also support
+    loading from bytecode, the optional methods specified directly by this ABC
+    is required.
+
+    Inherited abstractmethods not implemented in this ABC:
+
+        * ResourceLoader.get_data
+        * ExecutionLoader.get_filename
+
+    """
+
+    def path_mtime(self, path):
+        """Return the (int) modification time for the path (str)."""
+        if self.path_stats.__func__ is SourceLoader.path_stats:
+            raise IOError
+        return int(self.path_stats(path)['mtime'])
+
+    def path_stats(self, path):
+        """Return a metadata dict for the source pointed to by the path (str).
+        Possible keys:
+        - 'mtime' (mandatory) is the numeric timestamp of last source
+          code modification;
+        - 'size' (optional) is the size in bytes of the source code.
+        """
+        if self.path_mtime.__func__ is SourceLoader.path_mtime:
+            raise IOError
+        return {'mtime': self.path_mtime(path)}
+
+    def set_data(self, path, data):
+        """Write the bytes to the path (if possible).
+
+        Accepts a str path and data as bytes.
+
+        Any needed intermediary directories are to be created. If for some
+        reason the file cannot be written because of permissions, fail
+        silently.
+        """
+
+_register(SourceLoader, machinery.SourceFileLoader)

third_party/python/Lib/importlib/machinery.py

@@ -0,0 +1,21 @@
+"""The machinery of importlib: finders, loaders, hooks, etc."""
+
+import _imp
+
+from ._bootstrap import ModuleSpec
+from ._bootstrap import BuiltinImporter
+from ._bootstrap import FrozenImporter
+from ._bootstrap_external import (SOURCE_SUFFIXES, DEBUG_BYTECODE_SUFFIXES,
+                     OPTIMIZED_BYTECODE_SUFFIXES, BYTECODE_SUFFIXES,
+                     EXTENSION_SUFFIXES)
+from ._bootstrap_external import WindowsRegistryFinder
+from ._bootstrap_external import PathFinder
+from ._bootstrap_external import FileFinder
+from ._bootstrap_external import SourceFileLoader
+from ._bootstrap_external import SourcelessFileLoader
+from ._bootstrap_external import ExtensionFileLoader
+
+
+def all_suffixes():
+    """Returns a list of all recognized module suffixes for this process"""
+    return SOURCE_SUFFIXES + BYTECODE_SUFFIXES + EXTENSION_SUFFIXES

third_party/python/Lib/importlib/util.py

@@ -0,0 +1,288 @@
+"""Utility code for constructing importers, etc."""
+from . import abc
+from ._bootstrap import module_from_spec
+from ._bootstrap import _resolve_name
+from ._bootstrap import spec_from_loader
+from ._bootstrap import _find_spec
+from ._bootstrap_external import MAGIC_NUMBER
+from ._bootstrap_external import cache_from_source
+from ._bootstrap_external import decode_source
+from ._bootstrap_external import source_from_cache
+from ._bootstrap_external import spec_from_file_location
+
+from contextlib import contextmanager
+import functools
+import sys
+import types
+import warnings
+
+
+def resolve_name(name, package):
+    """Resolve a relative module name to an absolute one."""
+    if not name.startswith('.'):
+        return name
+    elif not package:
+        raise ValueError(f'no package specified for {repr(name)} '
+                         '(required for relative module names)')
+    level = 0
+    for character in name:
+        if character != '.':
+            break
+        level += 1
+    return _resolve_name(name[level:], package, level)
+
+
+def _find_spec_from_path(name, path=None):
+    """Return the spec for the specified module.
+
+    First, sys.modules is checked to see if the module was already imported. If
+    so, then sys.modules[name].__spec__ is returned. If that happens to be
+    set to None, then ValueError is raised. If the module is not in
+    sys.modules, then sys.meta_path is searched for a suitable spec with the
+    value of 'path' given to the finders. None is returned if no spec could
+    be found.
+
+    Dotted names do not have their parent packages implicitly imported. You will
+    most likely need to explicitly import all parent packages in the proper
+    order for a submodule to get the correct spec.
+
+    """
+    if name not in sys.modules:
+        return _find_spec(name, path)
+    else:
+        module = sys.modules[name]
+        if module is None:
+            return None
+        try:
+            spec = module.__spec__
+        except AttributeError:
+            raise ValueError('{}.__spec__ is not set'.format(name)) from None
+        else:
+            if spec is None:
+                raise ValueError('{}.__spec__ is None'.format(name))
+            return spec
+
+
+def find_spec(name, package=None):
+    """Return the spec for the specified module.
+
+    First, sys.modules is checked to see if the module was already imported. If
+    so, then sys.modules[name].__spec__ is returned. If that happens to be
+    set to None, then ValueError is raised. If the module is not in
+    sys.modules, then sys.meta_path is searched for a suitable spec with the
+    value of 'path' given to the finders. None is returned if no spec could
+    be found.
+
+    If the name is for submodule (contains a dot), the parent module is
+    automatically imported.
+
+    The name and package arguments work the same as importlib.import_module().
+    In other words, relative module names (with leading dots) work.
+
+    """
+    fullname = resolve_name(name, package) if name.startswith('.') else name
+    if fullname not in sys.modules:
+        parent_name = fullname.rpartition('.')[0]
+        if parent_name:
+            # Use builtins.__import__() in case someone replaced it.
+            parent = __import__(parent_name, fromlist=['__path__'])
+            return _find_spec(fullname, parent.__path__)
+        else:
+            return _find_spec(fullname, None)
+    else:
+        module = sys.modules[fullname]
+        if module is None:
+            return None
+        try:
+            spec = module.__spec__
+        except AttributeError:
+            raise ValueError('{}.__spec__ is not set'.format(name)) from None
+        else:
+            if spec is None:
+                raise ValueError('{}.__spec__ is None'.format(name))
+            return spec
+
+
+@contextmanager
+def _module_to_load(name):
+    is_reload = name in sys.modules
+
+    module = sys.modules.get(name)
+    if not is_reload:
+        # This must be done before open() is called as the 'io' module
+        # implicitly imports 'locale' and would otherwise trigger an
+        # infinite loop.
+        module = type(sys)(name)
+        # This must be done before putting the module in sys.modules
+        # (otherwise an optimization shortcut in import.c becomes wrong)
+        module.__initializing__ = True
+        sys.modules[name] = module
+    try:
+        yield module
+    except Exception:
+        if not is_reload:
+            try:
+                del sys.modules[name]
+            except KeyError:
+                pass
+    finally:
+        module.__initializing__ = False
+
+
+def set_package(fxn):
+    """Set __package__ on the returned module.
+
+    This function is deprecated.
+
+    """
+    @functools.wraps(fxn)
+    def set_package_wrapper(*args, **kwargs):
+        warnings.warn('The import system now takes care of this automatically.',
+                      DeprecationWarning, stacklevel=2)
+        module = fxn(*args, **kwargs)
+        if getattr(module, '__package__', None) is None:
+            module.__package__ = module.__name__
+            if not hasattr(module, '__path__'):
+                module.__package__ = module.__package__.rpartition('.')[0]
+        return module
+    return set_package_wrapper
+
+
+def set_loader(fxn):
+    """Set __loader__ on the returned module.
+
+    This function is deprecated.
+
+    """
+    @functools.wraps(fxn)
+    def set_loader_wrapper(self, *args, **kwargs):
+        warnings.warn('The import system now takes care of this automatically.',
+                      DeprecationWarning, stacklevel=2)
+        module = fxn(self, *args, **kwargs)
+        if getattr(module, '__loader__', None) is None:
+            module.__loader__ = self
+        return module
+    return set_loader_wrapper
+
+
+def module_for_loader(fxn):
+    """Decorator to handle selecting the proper module for loaders.
+
+    The decorated function is passed the module to use instead of the module
+    name. The module passed in to the function is either from sys.modules if
+    it already exists or is a new module. If the module is new, then __name__
+    is set the first argument to the method, __loader__ is set to self, and
+    __package__ is set accordingly (if self.is_package() is defined) will be set
+    before it is passed to the decorated function (if self.is_package() does
+    not work for the module it will be set post-load).
+
+    If an exception is raised and the decorator created the module it is
+    subsequently removed from sys.modules.
+
+    The decorator assumes that the decorated function takes the module name as
+    the second argument.
+
+    """
+    warnings.warn('The import system now takes care of this automatically.',
+                  DeprecationWarning, stacklevel=2)
+    @functools.wraps(fxn)
+    def module_for_loader_wrapper(self, fullname, *args, **kwargs):
+        with _module_to_load(fullname) as module:
+            module.__loader__ = self
+            try:
+                is_package = self.is_package(fullname)
+            except (ImportError, AttributeError):
+                pass
+            else:
+                if is_package:
+                    module.__package__ = fullname
+                else:
+                    module.__package__ = fullname.rpartition('.')[0]
+            # If __package__ was not set above, __import__() will do it later.
+            return fxn(self, module, *args, **kwargs)
+
+    return module_for_loader_wrapper
+
+
+class _LazyModule(types.ModuleType):
+
+    """A subclass of the module type which triggers loading upon attribute access."""
+
+    def __getattribute__(self, attr):
+        """Trigger the load of the module and return the attribute."""
+        # All module metadata must be garnered from __spec__ in order to avoid
+        # using mutated values.
+        # Stop triggering this method.
+        self.__class__ = types.ModuleType
+        # Get the original name to make sure no object substitution occurred
+        # in sys.modules.
+        original_name = self.__spec__.name
+        # Figure out exactly what attributes were mutated between the creation
+        # of the module and now.
+        attrs_then = self.__spec__.loader_state['__dict__']
+        original_type = self.__spec__.loader_state['__class__']
+        attrs_now = self.__dict__
+        attrs_updated = {}
+        for key, value in attrs_now.items():
+            # Code that set the attribute may have kept a reference to the
+            # assigned object, making identity more important than equality.
+            if key not in attrs_then:
+                attrs_updated[key] = value
+            elif id(attrs_now[key]) != id(attrs_then[key]):
+                attrs_updated[key] = value
+        self.__spec__.loader.exec_module(self)
+        # If exec_module() was used directly there is no guarantee the module
+        # object was put into sys.modules.
+        if original_name in sys.modules:
+            if id(self) != id(sys.modules[original_name]):
+                raise ValueError(f"module object for {original_name!r} "
+                                  "substituted in sys.modules during a lazy "
+                                  "load")
+        # Update after loading since that's what would happen in an eager
+        # loading situation.
+        self.__dict__.update(attrs_updated)
+        return getattr(self, attr)
+
+    def __delattr__(self, attr):
+        """Trigger the load and then perform the deletion."""
+        # To trigger the load and raise an exception if the attribute
+        # doesn't exist.
+        self.__getattribute__(attr)
+        delattr(self, attr)
+
+
+class LazyLoader(abc.Loader):
+
+    """A loader that creates a module which defers loading until attribute access."""
+
+    @staticmethod
+    def __check_eager_loader(loader):
+        if not hasattr(loader, 'exec_module'):
+            raise TypeError('loader must define exec_module()')
+
+    @classmethod
+    def factory(cls, loader):
+        """Construct a callable which returns the eager loader made lazy."""
+        cls.__check_eager_loader(loader)
+        return lambda *args, **kwargs: cls(loader(*args, **kwargs))
+
+    def __init__(self, loader):
+        self.__check_eager_loader(loader)
+        self.loader = loader
+
+    def create_module(self, spec):
+        return self.loader.create_module(spec)
+
+    def exec_module(self, module):
+        """Make the module load lazily."""
+        module.__spec__.loader = self.loader
+        module.__loader__ = self.loader
+        # Don't need to worry about deep-copying as trying to set an attribute
+        # on an object would have triggered the load,
+        # e.g. ``module.__spec__.loader = None`` would trigger a load from
+        # trying to access module.__spec__.
+        loader_state = {}
+        loader_state['__dict__'] = module.__dict__.copy()
+        loader_state['__class__'] = module.__class__
+        module.__spec__.loader_state = loader_state
+        module.__class__ = _LazyModule