Check timeout type in KafkaClient constructor

If a future was passed as the only positional parameter it would
be assigned to the "timeout_ms" parameter erroneously. This mistake
would not raise any exception but would lead to odd behaviour later,
what could make it extremely difficult to troubleshoot.

Adding a type check ensures that an exception is raise earlier to
notify the user about the problem.

Author: asdaraujo

kafka/client_async.py

@@ -526,6 +526,8 @@ def poll(self, timeout_ms=None, future=None, delayed_tasks=True):
             timeout_ms = 100
         elif timeout_ms is None:
             timeout_ms = self.config['request_timeout_ms']
+        elif not isinstance(timeout_ms, int) and not isinstance(timeout_ms, float):
+            raise RuntimeError('Invalid type for timeout: %s' % (type(timeout_ms),))
 
         responses = []