Switch to pytest_container devel branch

Author: dcermak

tox.ini

@@ -13,7 +13,7 @@ deps =
     requests
     # 8.4.0 is borked: https://github.com/jd/tenacity/issues/471
     tenacity != 8.4.0
-    git+https://github.com/dcermak/pytest_container
+    git+https://github.com/dcermak/pytest_container@volumes-classes-immutable
     doc: Sphinx
 
 [testenv]