force pytest to a sufficiently modern version

Leif Johansson · Leif Johansson · commit 94a970a3e495 · 2021-04-20T22:59:34.000+02:00
diff --git a/test_requirements.txt b/test_requirements.txt
@@ -5,7 +5,7 @@ isort
 mako
 mock
 pbr
-pytest
+pytest>=6.0.0
 pytest-cov
 setuptools
 wsgi_intercept
