Fixed #21869 -- Fixed docs building with Sphinx 1.2.1.

Thanks tragiclifestories for the report.

docs/_ext/djangodocs.py

@@ -236,11 +236,13 @@ def depart_table(self, node):
         self.compact_p = self.context.pop()
         self.body.append('</table>\n')
 
-    # <big>? Really?
     def visit_desc_parameterlist(self, node):
-        self.body.append('(')
+        self.body.append('(')  # by default sphinx puts <big> around the "("
         self.first_param = 1
+        self.optional_param_level = 0
         self.param_separator = node.child_text_separator
+        self.required_params_left = sum([isinstance(c, addnodes.desc_parameter)
+                                         for c in node.children])
 
     def depart_desc_parameterlist(self, node):
         self.body.append(')')