From Fedora Project Wiki
Python Packages (pypi)
As Pypi has moved to storing files in directories which change depending on the file being stored, it is rather unpleasant to use in a Source: URL. Instead, files.pythonhosted.org can be used as follows, where <name> is the project's name on Pypi and <first_letter> is the first letter in that name. (See also the sample python spec here).
Source0: https://files.pythonhosted.org/packages/source/<first_letter>/<name>/<name>-%{version}.tar.gz