Also provide pythonXdist() with PEP 503 normalized names (#1791530)

That is, we add new provides that replace dots with a dash.

Package that used to provide python3dist(zope.component) and python3.8dist(zope.component)
now also provides python3dist(zope-component) and python3.8dist(zope-component).

Package that used to provide python3dist(a.-.-.-.a) now provides python3dist(a-a) as well.

This is consistent with pip behavior, `pip install zope-component` installs zope.component.

Historically, we have always used dist.key (safe_name) from setuptools,
but that is a non-standardized convention -- whether or not it replaces dots
with dashes is not even documented.
We say we use "canonical name" or "normalized name" everywhere, yet we didn't.

We really need to follow the standard (PEP 503):

https://www.python.org/dev/peps/pep-0503/#normalized-names

The proper function here would be packaging.utils.canonicalize_name
https://packaging.pypa.io/en/latest/utils/#packaging.utils.canonicalize_name
-- we reimplement it here to avoid an external dependency.

This is the first required step needed if we want to change our requirements later.
If we decide we don't, for whatever reason, this doesn't break anything.

python-rpm-generators.spec

@@ -5,7 +5,7 @@
 Name:           python-rpm-generators
 Summary:        Dependency generators for Python RPMs
 Version:        10
-Release:        2%{?dist}
+Release:        3%{?dist}
 
 # Originally all those files were part of RPM, so license is kept here
 License:        GPLv2+
@@ -49,6 +49,9 @@ install -Dpm0755 -t %{buildroot}%{_rpmconfigdir} pythondeps.sh pythondistdeps.py
 %{_rpmconfigdir}/pythondistdeps.py
 
 %changelog
+* Fri Jan 17 2020 Miro Hrončok <mhroncok@redhat.com> - 10-3
+- Also provide pythonXdist() with PEP 503 normalized names (#1791530)
+
 * Fri Jan 03 2020 Miro Hrončok <mhroncok@redhat.com> - 10-2
 - Fix more complicated requirement expressions by adding parenthesis