fix SyntaxWarning 'is not' when checking for equality

Signed-off-by: Mikael Arguedas <[email protected]>

smach/smach/state_machine.py

@@ -74,7 +74,7 @@ def __init__(self, outcomes, input_keys=[], output_keys=[]):
 
     ### Getter and Setter to allow pickling and unpickling state machines
     def __getstate__(self):
-        return {k:v for (k, v) in self.__dict__.items() if k is not "_state_transitioning_lock"}
+        return {k:v for (k, v) in self.__dict__.items() if k != "_state_transitioning_lock"}
 
     def __setstate__(self, d):
         self.__dict__ = d