Raise NotImplementedError instead of NotImplemented

NotImplementedError is the name of the exception
(https://docs.python.org/2/library/exceptions.html).
NotImplemented is the name of a constant
(https://docs.python.org/2/library/constants.html).

This patch fix it.

Change-Id: Icfbc0603d03e2001d1494027c492059687e15fa7
Closes-Bug: #1339855

keystoneauth1/extras/_saml2/v3/saml2.py

@@ -227,7 +227,7 @@ class _FederatedSaml(v3.FederationBaseAuth):
 
     @abc.abstractmethod
     def get_requests_auth(self):
-        raise NotImplemented()
+        raise NotImplementedError()
 
     def get_unscoped_auth_ref(self, session, **kwargs):
         method = self.get_requests_auth()

keystoneauth1/identity/v3/base.py

@@ -194,7 +194,7 @@ class Auth(BaseAuth):
         for method in self.auth_methods:
             try:
                 elements = method.get_cache_id_elements()
-            except NotImplemented:
+            except NotImplementedError:
                 return None
 
             params.update(elements)
@@ -259,7 +259,7 @@ class AuthMethod(object):
         should be prefixed with the plugin identifier. For example the password
         plugin returns its username value as 'password_username'.
         """
-        raise NotImplemented()
+        raise NotImplementedError()
 
 
 @six.add_metaclass(abc.ABCMeta)

keystoneauth1/identity/v3/oidc.py

@@ -280,7 +280,7 @@ class _OidcBase(federation.FederationBaseAuth):
         :returns: a python dictionary containing the payload to be exchanged
         :rtype: dict
         """
-        raise NotImplemented()
+        raise NotImplementedError()
 
 
 class OidcPassword(_OidcBase):

keystoneauth1/loading/base.py

@@ -104,7 +104,7 @@ class BaseLoader(object):
 
     @property
     def plugin_class(self):
-        raise NotImplemented()
+        raise NotImplementedError()
 
     def create_plugin(self, **kwargs):
         """Create a plugin from the options available for the loader.