Fix offset commits when using 0.8 brokers

Author: dpkp

kafka/coordinator/consumer.py

@@ -538,7 +538,7 @@ def _send_offset_commit_request(self, offsets):
         # if the generation is None, we are not part of an active group
         # (and we expect to be). The only thing we can do is fail the commit
         # and let the user rejoin the group in poll()
-        if generation is None:
+        if self.config['api_version'] >= (0, 9) and generation is None:
             return Future().failure(Errors.CommitFailedError())
 
         if self.config['api_version'] >= (0, 9):
@@ -557,9 +557,7 @@ def _send_offset_commit_request(self, offsets):
             )
         elif self.config['api_version'] >= (0, 8, 2):
             request = OffsetCommitRequest[1](
-                self.group_id,
-                generation.generation_id,
-                generation.member_id,
+                self.group_id, -1, '',
                 [(
                     topic, [(
                         partition,