Remove sleep check when no partitions assigned -- no longer needed

kafka/consumer/group.py

@@ -1070,16 +1070,6 @@ def _message_generator(self):
             # like heartbeats, auto-commits, and metadata refreshes
             timeout_at = self._next_timeout()
 
-            # Because the consumer client poll does not sleep unless blocking on
-            # network IO, we need to explicitly sleep when we know we are idle
-            # because we haven't been assigned any partitions to fetch / consume
-            if self._use_consumer_group() and not self.assignment():
-                sleep_time = max(timeout_at - time.time(), 0)
-                if sleep_time > 0 and not self._client.in_flight_request_count():
-                    log.debug('No partitions assigned; sleeping for %s', sleep_time)
-                    time.sleep(sleep_time)
-                    continue
-
             # Short-circuit the fetch iterator if we are already timed out
             # to avoid any unintentional interaction with fetcher setup
             if time.time() > timeout_at: