fixed TestRemoteRobot.teardown_class()

--HG--
branch : dev

Author: userzimmermann

test/remote/test_remote.py

@@ -89,7 +89,7 @@ def teardown_class(cls):
         """Ensures that the ``RemoteRobot`` process
         is really terminated in the end.
         """
-        if not cls.process.poll():
+        if cls.process.poll() is None:
             cls.process.terminate()