setup: Update the minimum required runtime python3 version

Related to T2367

setup.py

+# Copyright (C) 2016-2020  The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
 from setuptools import setup, find_packages
 
 setup(
     name='swh-sandbox',
     description='Sandbox project',
+    python_requires=">=3.7",
     version='0.0.3',
     author='Software Heritage developers',
     author_email='swh-devel@inria.fr',

[Phabricator Migration user]

Some references in the commit message have been migrated:

• T2367 is now swh-core#2367 (closed)