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}'

tests/data/scripts_pythonbundles/pip.in

@@ -0,0 +1,24 @@
+appdirs==1.4.3
+CacheControl==0.12.6
+colorama==0.4.3
+contextlib2==0.6.0.post1
+distlib==0.3.0
+distro==1.5.0
+html5lib==1.0.1
+ipaddress==1.0.23  # Only needed on 2.6 and 2.7
+msgpack==1.0.0
+packaging==20.3
+pep517==0.8.2
+progress==1.5
+pyparsing==2.4.7
+requests==2.23.0
+    certifi==2020.04.05.1
+    chardet==3.0.4
+    idna==2.9
+    urllib3==1.25.8
+resolvelib==0.3.0
+retrying==1.3.3
+setuptools==44.0.0
+six==1.14.0
+toml==0.10.0
+webencodings==0.5.1