restrict supported python versions through package metadata

Signed-off-by: oleg.hoefling <oleg.hoefling@gmail.com>

Author: hoefling

setup.py

@@ -428,6 +428,7 @@ def prepare_static_build_linux(self):
     long_description=long_desc,
     ext_modules=[pyxmlsec],
     cmdclass={'build_ext': build_ext},
+    python_requires='>=2.7, !=3.0.*, !=3.1.*, !=3.2.*, !=3.3.*, !=3.4.*',
     setup_requires=setup_reqs,
     install_requires=['lxml>=3.8'],
     author="Bulat Gaifullin",