Fix invocation with Python 3.9 (#1798929)

Backported from Fedora 31:
https://src.fedoraproject.org/rpms/python-tox/c/aa466cd2d67b5ca7e5f4f58d0fbc704b38c97d94?branch=f31

Added 3.10 and 3.11 as well.

With this tox.ini:

    [tox]
    skipsdist = True
    [testenv]
    commands = python -c 'import sys; print(sys.version)'

Before:

    $ tox -e py39
    ...
    3.6.8 (default, Aug 24 2020, 17:57:11)
    ...
      py39: commands succeeded
      congratulations :)

After:

    $ tox -e py39
    ...
    3.9.1 (default, Jan 18 2021, 16:14:01)
    ...
      py39: commands succeeded
      congratulations :)

The Python 3.10+ addition remains untested, as I have no Python 3.10+ build for EL 8 available.

python-tox.spec

@@ -2,11 +2,16 @@
 
 Name:           python-%{srcname}
 Version:        3.4.0
-Release:        1%{?dist}
+Release:        2%{?dist}
 Summary:        Virtualenv-based automation of test activities
 License:        MIT
 URL:            https://tox.readthedocs.io
 Source0:        %{pypi_source}
+
+# Run py39 env with Python 3.9
+# https://bugzilla.redhat.com/show_bug.cgi?id=1798929
+Patch1:         py39.patch
+
 BuildArch:      noarch
 
 %description
@@ -46,7 +51,7 @@ can use for:
    boilerplate and merging CI and shell-based testing.
 
 %prep
-%setup -q -n %{srcname}-%{version}
+%autosetup -p1 -n %{srcname}-%{version}
 
 # remove bundled egg-info
 rm -rf %{srcname}.egg-info
@@ -65,6 +70,9 @@ rm -rf %{srcname}.egg-info
 %{python3_sitelib}/%{srcname}-%{version}-py%{python3_version}.egg-info
 
 %changelog
+* Tue Jan 19 2021 Miro Hrončok <mhroncok@redhat.com> - 3.4.0-2
+- Fix invocation with Python 3.9 (#1798929)
+
 * Tue Feb 25 2020 Gris Ge <fge@redhat.com> - 3.4.0-1
 - Port to EPEL8