We have to keep it anyway for 3.6, 3.7, 3.8, 3.9

Author: StanFromIreland

tox.ini

@@ -7,7 +7,7 @@ skip_missing_interpreters = true
 description = Test that the tzdata contents are accessible
 deps =
     pytest
-    pytest-subtests; python_version>='3.6'
+    pytest-subtests; python_version >= '3.6' and python_version <= '3.9'
     importlib_resources; python_version<'3.7'
 commands =
     pytest {toxinidir} {posargs}