Python library: should depend on setuptools or otherwise replace `pkg_resources`

[juanmirocks]

The python asts package depends internally on pkg_resources (which is deprecated).

If still used, at least the setuptools package should be declared as a dependency. Otherwise, trying to pip-install & import asts, results in:

ModuleNotFoundError: No module named 'pkg_resources'

[rafa-br34]

Same problem here.