fixup! Added support for client_credentials grant type

Author: clintonb

provider/views.py

@@ -41,6 +41,7 @@ class AccessTokenMixin(object):
     These methods may be used by both Authorization and Access Token endpoints.
     """
 
+    @abc.abstractmethod
     def get_access_token(self, request, user, scope, client):
         """
         Override to handle fetching of an existing access token.
@@ -49,6 +50,7 @@ def get_access_token(self, request, user, scope, client):
         """
         raise NotImplementedError  # pragma: no cover
 
+    @abc.abstractmethod
     def create_access_token(self, request, user, scope, client):
         """
         Override to handle access token creation.
@@ -57,6 +59,7 @@ def create_access_token(self, request, user, scope, client):
         """
         raise NotImplementedError  # pragma: no cover
 
+    @abc.abstractmethod
     def create_refresh_token(self, request, user, scope, access_token, client):
         """
         Override to handle refresh token creation.
@@ -65,6 +68,7 @@ def create_refresh_token(self, request, user, scope, access_token, client):
         """
         raise NotImplementedError  # pragma: no cover
 
+    @abc.abstractmethod
     def invalidate_refresh_token(self, refresh_token):
         """
         Override to handle refresh token invalidation. When requesting a new
@@ -74,6 +78,7 @@ def invalidate_refresh_token(self, refresh_token):
         """
         raise NotImplementedError  # pragma: no cover
 
+    @abc.abstractmethod
     def invalidate_access_token(self, access_token):
         """
         Override to handle access token invalidation. When a new access token