Fixed #24621 -- Fixed and documented SessionBase.pop's second argument

Changed SessionBase.pop's second argument to explicitly be default=None
rather than *args since _session is always a dict. Thanks gabor for the
report and Tim Graham for the review.

django/contrib/sessions/backends/base.py

@@ -58,9 +58,9 @@ class SessionBase(object):
     def get(self, key, default=None):
         return self._session.get(key, default)
 
-    def pop(self, key, *args):
+    def pop(self, key, default=None):
         self.modified = self.modified or key in self._session
-        return self._session.pop(key, *args)
+        return self._session.pop(key, default)
 
     def setdefault(self, key, value):
         if key in self._session:

docs/topics/http/sessions.txt

@@ -205,9 +205,9 @@ You can edit it multiple times.
 
       Example: ``fav_color = request.session.get('fav_color', 'red')``
 
-    .. method:: pop(key)
+    .. method:: pop(key, default=None)
 
-      Example: ``fav_color = request.session.pop('fav_color')``
+      Example: ``fav_color = request.session.pop('fav_color', 'blue')``
 
     .. method:: keys()