parse "extra" for dependencies that specify Python versions
PyPI packages sometimes declare a dependency only for a certain Python version, for example: "typing ; python_version < "3.5""
Currently, pypi-upt does not parse this (it's listed as a TODO in upt-macports.py and currently only done for test-dependencies) and it would not return this dependency at all. Examples of packages where this happens are "astroid" and "django-extensions".
Of course, it would be great to have this implemented across all dependency types. But, until we parse Python versions for runtime dependencies, would it make sense to just always return such dependency instead of ignoring it?