Add base class for Meddleware

Created a BaseMeddleware which all Meddleware should derive
from. This is not strictly needed, but will greatly help.

The base class has the common __init__ of all the other
Meddlwares and fall backs for all hooks. That way a new
Meddlware only needs to override what it actually wants to
implement.

mediagoblin/meddleware/__init__.py

@@ -18,3 +18,15 @@ ENABLED_MEDDLEWARE = (
     'mediagoblin.meddleware.noop:NoOpMeddleware',
     'mediagoblin.meddleware.csrf:CsrfMeddleware',
     )
+
+
+class BaseMeddleware(object):
+
+    def __init__(self, mg_app):
+        self.app = mg_app
+
+    def process_request(self, request):
+        pass
+
+    def process_response(self, request, response):
+        pass

mediagoblin/meddleware/csrf.py

@@ -21,6 +21,7 @@ from webob.exc import HTTPForbidden
 from wtforms import Form, HiddenField, validators
 
 from mediagoblin import mg_globals
+from mediagoblin.meddleware import BaseMeddleware
 
 # Use the system (hardware-based) random number generator if it exists.
 # -- this optimization is lifted from Django
@@ -47,7 +48,7 @@ def render_csrf_form_token(request):
     return form.csrf_token
 
 
-class CsrfMeddleware(object):
+class CsrfMeddleware(BaseMeddleware):
     """CSRF Protection Meddleware
 
     Adds a CSRF Cookie to responses and verifies that it is present
@@ -57,9 +58,6 @@ class CsrfMeddleware(object):
     CSRF_KEYLEN = 64
     SAFE_HTTP_METHODS = ("GET", "HEAD", "OPTIONS", "TRACE")
 
-    def __init__(self, mg_app):
-        self.app = mg_app
-
     def process_request(self, request):
         """For non-safe requests, confirm that the tokens are present
         and match.

mediagoblin/meddleware/noop.py

@@ -15,11 +15,10 @@
 # along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 
-class NoOpMeddleware(object):
+from mediagoblin.meddleware import BaseMeddleware
 
-    def __init__(self, mg_app):
-        self.app = mg_app
 
+class NoOpMeddleware(BaseMeddleware):
     def process_request(self, request):
         pass