Python versions that don't provide SSLContext.load_default_certs can't load system CA certificates on Windows. The wincertstore package on pypi could be used to solve that problem:

https://pypi.python.org/pypi/wincertstore

Python versions that don't provide SSLContext can't load system CA certificates on any platform. Instead we could optionally load the Mozilla CA bundle through certifi as a last resort:

https://pypi.python.org/pypi/certifi