tests: perform a shallow copy instead of a deep copy Python 3 can't perform a deep copy because it looks like symbols in the locals() namespace are not deep-copyable. For the curious, somehow the deepcopy() is attempting to copy objects attached to the unittest.* functions for the running test! We don't use deepcopy() anywhere in the code base and a shallow object copy should be sufficient to test lock copying. Actually, I'm not sure why we even test this, as I couldn't find copy.copy() being used for lock copying either. Who knows. Differential Revision: https://phab.mercurial-scm.org/D5770