Test and improve the synchronization code

[kurtmckee]

Added

• Add tests to bring Synchronization.py to 100% coverage
• Add type annotations to the synchronization primitives
• Add typing_extensions as a Python 3.9 requirement; this is needed to annotate that the synchronized() decorator takes a function with a certain set of parameter and return types and returns a function with the same parameter and return types

Changed

• Make the synchronized function's self parameter explicit; this allows the self parameter to be type-annotated so the dependency on the self.mutex attribute is explicit
• Use the self.mutex lock as a context manager
• Support keyword arguments to synchronized functions

Fixed

• Wrap synchronized functions correctly; previous behavior was to lose the function name and docstring

Removed

• Remove print() lines that are commented out
• Remove a bytes instance check; method names can only be strings

[coveralls]

coverage: 64.919% (+0.3%) from 64.591% when pulling d984eecf0e3481c9c80b3d6921ca19d43b9da2f4 on kurtmckee:test-synchronization into f162aa2f646863fad62599378be67c5b31fd751f on LudovicRousseau:master.

[LudovicRousseau]

Thanks