Drop python2 support

See also nexedi/slapos@4230cd1b

CHANGES.txt

+0.135 (Unreleased)
+==================
+
+* This release drops support for python2. Software releases using python2
+are pinned to 0.128, the last version with tests passing on python2
+
 0.134 (2023-03-09)
 ==================
 

setup.py

@@ -29,7 +29,7 @@ setup(name=name,
       maintainer="Nexedi",
       maintainer_email="info@nexedi.com",
       url="https://lab.nexedi.com/nexedi/slapos.toolbox",
-      python_requires='>=2.7',
+      python_requires='>=3.8',
       install_requires=(
         'Flask', # needed by servers
         'atomize', # needed by pubsub