minor tweaks to get authentication working

Author: Lars Jørgen Solberg

kafka/conn.py

@@ -299,7 +299,7 @@ def _try_handshake(self):
         return False
 
     def _try_authenticate(self):
-        assert self.config['api_version'] >= (0, 10) or self.config['api_version'] is None
+        assert self.config['api_version'] is None or self.config['api_version'] >= (0, 10)
 
         if self._sasl_auth_future is None:
             # Build a SaslHandShakeRequest message
@@ -311,7 +311,7 @@ def _try_authenticate(self):
             self._sasl_auth_future = future
         self._recv()
         if self._sasl_auth_future.failed():
-            raise self._sasl_auth_future.exception
+            raise self._sasl_auth_future.exception # pylint: disable-msg=raising-bad-type
         return self._sasl_auth_future.succeeded()
 
     def _handle_sasl_handshake_response(self, future, response):
@@ -345,25 +345,24 @@ def _try_authenticate_plain(self, future):
 
             # The server will send a zero sized message (that is Int32(0)) on success.
             # The connection is closed on failure
-            received_bytes = 0
-            while received_bytes < 4:
-                data += self._sock.recv(4 - received_bytes)
-                received_bytes += len(data)
-                if not data:
+            while len(data) < 4:
+                fragment = self._sock.recv(4 - len(data))
+                if not fragment:
                     log.error('%s: Authentication failed for user %s', self, self.config['sasl_plain_username'])
                     error = Errors.AuthenticationFailedError(
                         'Authentication failed for user {0}'.format(
                             self.config['sasl_plain_username']))
                     future.failure(error)
                     raise error
+                data += fragment
             self._sock.setblocking(False)
         except (AssertionError, ConnectionError) as e:
             log.exception("%s: Error receiving reply from server",  self)
             error = Errors.ConnectionError("%s: %s" % (str(self), e))
             future.failure(error)
             self.close(error=error)
 
-        if data != '\x00\x00\x00\x00':
+        if data != b'\x00\x00\x00\x00':
             return future.failure(Errors.AuthenticationFailedError())
 
         return future.success(True)