Fix Python2/Python3 incompatibility

map() function is lazy in python3
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failed #1118
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    class Callable(extra=collections_abc.Callable, metaclass=CallableMeta):
File "/usr/local/lib/python3.7/dist-packages/typing.py", line 1007, in __new__
self._abc_registry = extra._abc_registry
AttributeError: type object 'Callable' has no attribute '_abc_registry'
Makefile:23: recipe for target 'flake8' failed
make: *** [flake8] Error 1
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