python-3.6.zip added from Github

README.cosmo contains the necessary links.

third_party/python/Lib/lib2to3/fixes/fix_except.py

@@ -0,0 +1,93 @@
+"""Fixer for except statements with named exceptions.
+
+The following cases will be converted:
+
+- "except E, T:" where T is a name:
+
+    except E as T:
+
+- "except E, T:" where T is not a name, tuple or list:
+
+        except E as t:
+            T = t
+
+    This is done because the target of an "except" clause must be a
+    name.
+
+- "except E, T:" where T is a tuple or list literal:
+
+        except E as t:
+            T = t.args
+"""
+# Author: Collin Winter
+
+# Local imports
+from .. import pytree
+from ..pgen2 import token
+from .. import fixer_base
+from ..fixer_util import Assign, Attr, Name, is_tuple, is_list, syms
+
+def find_excepts(nodes):
+    for i, n in enumerate(nodes):
+        if n.type == syms.except_clause:
+            if n.children[0].value == 'except':
+                yield (n, nodes[i+2])
+
+class FixExcept(fixer_base.BaseFix):
+    BM_compatible = True
+
+    PATTERN = """
+    try_stmt< 'try' ':' (simple_stmt | suite)
+                  cleanup=(except_clause ':' (simple_stmt | suite))+
+                  tail=(['except' ':' (simple_stmt | suite)]
+                        ['else' ':' (simple_stmt | suite)]
+                        ['finally' ':' (simple_stmt | suite)]) >
+    """
+
+    def transform(self, node, results):
+        syms = self.syms
+
+        tail = [n.clone() for n in results["tail"]]
+
+        try_cleanup = [ch.clone() for ch in results["cleanup"]]
+        for except_clause, e_suite in find_excepts(try_cleanup):
+            if len(except_clause.children) == 4:
+                (E, comma, N) = except_clause.children[1:4]
+                comma.replace(Name("as", prefix=" "))
+
+                if N.type != token.NAME:
+                    # Generate a new N for the except clause
+                    new_N = Name(self.new_name(), prefix=" ")
+                    target = N.clone()
+                    target.prefix = ""
+                    N.replace(new_N)
+                    new_N = new_N.clone()
+
+                    # Insert "old_N = new_N" as the first statement in
+                    #  the except body. This loop skips leading whitespace
+                    #  and indents
+                    #TODO(cwinter) suite-cleanup
+                    suite_stmts = e_suite.children
+                    for i, stmt in enumerate(suite_stmts):
+                        if isinstance(stmt, pytree.Node):
+                            break
+
+                    # The assignment is different if old_N is a tuple or list
+                    # In that case, the assignment is old_N = new_N.args
+                    if is_tuple(N) or is_list(N):
+                        assign = Assign(target, Attr(new_N, Name('args')))
+                    else:
+                        assign = Assign(target, new_N)
+
+                    #TODO(cwinter) stopgap until children becomes a smart list
+                    for child in reversed(suite_stmts[:i]):
+                        e_suite.insert_child(0, child)
+                    e_suite.insert_child(i, assign)
+                elif N.prefix == "":
+                    # No space after a comma is legal; no space after "as",
+                    # not so much.
+                    N.prefix = " "
+
+        #TODO(cwinter) fix this when children becomes a smart list
+        children = [c.clone() for c in node.children[:3]] + try_cleanup + tail
+        return pytree.Node(node.type, children)