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