DEV: Fix InvalidSpecifier issues with newer setuptools

Author: gerrymanoim

setup.cfg

@@ -41,7 +41,7 @@ keywords =
 [options]
 include_package_data = True
 packages = find:
-python_requires = '~=3.5'
+python_requires = ~=3.5
 setup_requires =
     setuptools
 install_requires =