Add a script to generate Python bundled provides
    
    See https://src.fedoraproject.org/rpms/python-setuptools/pull-request/40
    
    Strictly speaking, this is not an RPM generator, but:
    
     - it generates provides
     - it is tighly coupled with pythondistdeps.py
    
    Usage:
    
     1. Run `$ /usr/lib/rpm/pythonbundles.py .../vendored.txt`
    
     2. Copy the output into the spec as a macro definition:
    
        %global bundled %{expand:
        Provides: bundled(python3dist(appdirs)) = 1.4.3
        Provides: bundled(python3dist(packaging)) = 16.8
        Provides: bundled(python3dist(pyparsing)) = 2.2.1
        Provides: bundled(python3dist(six)) = 1.15
        }
    
     3. Use the macro to expand the provides
     4. Verify the macro contents in %check:
    
        %check
        ...
        %{_rpmconfigdir}/pythonbundles.py src/_vendor/vendored.txt --compare-with '%{bundled}'