Pull out database validation into validator class

util/config/validators/__init__.py

@@ -0,0 +1,20 @@
+from abc import ABCMeta, abstractmethod, abstractproperty
+from six import add_metaclass
+
+class ConfigValidationException(Exception):
+  """ Exception raised when the configuration fails to validate for a known reason. """
+  pass
+
+
+@add_metaclass(ABCMeta)
+class BaseValidator(object):
+  @abstractproperty
+  def name(self):
+    """ The key for the validation API. """
+    pass
+
+  @classmethod
+  @abstractmethod
+  def validate(cls, config, user, user_password):
+    """ Raises Exception if failure to validate. """
+    pass

util/config/validators/database.py

@@ -0,0 +1,18 @@
+from peewee import OperationalError
+
+from data.database import validate_database_url
+from util.config.validators import BaseValidator, ConfigValidationException
+
+class DatabaseValidator(BaseValidator):
+  name = "database"
+
+  @classmethod
+  def validate(cls, config, user, user_password):
+    """ Validates connecting to the database. """
+    try:
+      validate_database_url(config['DB_URI'], config.get('DB_CONNECTION_ARGS', {}))
+    except OperationalError as ex:
+      if ex.args and len(ex.args) > 1:
+        raise ConfigValidationException(ex.args[1])
+      else:
+        raise ex

util/config/validators/test/test_database.py

@@ -0,0 +1,21 @@
+import pytest
+
+from util.config.validators import ConfigValidationException
+from util.config.validators.database import DatabaseValidator
+
+@pytest.mark.parametrize('unvalidated_config,user,user_password,expected', [
+  (None, None, None, TypeError),
+  ({}, None, None, KeyError),
+  ({'DB_URI': 'sqlite:///:memory:'}, None, None, None),
+  ({'DB_URI': 'invalid:///:memory:'}, None, None, KeyError),
+  ({'DB_NOTURI': 'sqlite:///:memory:'}, None, None, KeyError),
+  ({'DB_URI': 'mysql:///someinvalid'}, None, None, ConfigValidationException),
+])
+def test_validate_database(unvalidated_config, user, user_password, expected):
+  validator = DatabaseValidator()
+
+  if expected is not None:
+    with pytest.raises(expected):
+      validator.validate(unvalidated_config, user, user_password)
+  else:
+    validator.validate(unvalidated_config, user, user_password)