Fix for Python 4: use >= 3 instead of == 3

[hugovk]

• wrote descriptive pull request text
• [n/a] added/updated test(s)
• [n/a] updated/extended the documentation
• [n/a] added news fragment in docs/changelog folder

We don't yet know if 3.10 or 4.0 will follow Python 3.9, but whichever it is, it will probably happen in 2020 when Python 3.9 reaches beta.

When run on Python 4, this line would be skipped:

    if sys.version_info[0] == 3:
        enablerlcompleter()	

Instead:

    if sys.version_info[0] >= 3:
        enablerlcompleter()	

Found using https://github.com/asottile/flake8-2020.

[gaborbernat]

We do, see https://www.python.org/dev/peps/pep-0596/#id6. Either way, we don't know if python 4 (if ever released) will be python 3 compatible, so what we have now is the correct thing to do.

After the release of 3.10.0 final, a final 3.9 bugfix update will be released.

[hugovk]

Still a draft, but that 3.9 release PEP looks fairly definitive. Some PEPs refer to 3.10, others to 4, so it's not entirely clear.

I also found this, and the consensus is towards 3.10:

• https://mail.python.org/pipermail/python-committers/2018-September/006152.html

Anyway, thanks!

[gaborbernat]

@hugovk side-note that we'll be soon dropping the master branch as a whole, and promoting the rewrite branch from #1366 (see https://github.com/pypa/virtualenv/milestone/7) - so would this need be fixed most likely would be on that branch either way