Readjusted to throw if Twython hasn't made a API call.

twython/twython.py

@@ -245,10 +245,8 @@ class Twython(object):
                 x-rate-limit-reset
         """
         if self._last_call is None:
-            if default_return_value is None:
             raise TwythonError('This function must be called after an API call.  It delivers header information.')
-            else:
-                return default_return_value
+        
                 
         return self._last_call['headers'].get(header, default_return_value)