Due to mypy, it's not possible to patch the value, so just be lenient…

… in access.

conftest.py

@@ -1,23 +1,13 @@
+import builtins
 import sys
 
-import pytest
 
+def pytest_configure():
+    add_future_flags()
 
-class Flags:
-    warn_default_encoding = 0
 
-    def __getattr__(self, *args):
-        return getattr(sys.flags, *args)
-
-
-@pytest.fixture(scope="session")
-def monkeysession():
-    with pytest.MonkeyPatch.context() as mp:
-        yield mp
-
-
-@pytest.fixture(scope="session", autouse=True)
-def future_flags(monkeysession):
+def add_future_flags():
     if sys.version_info > (3, 10):
         return
-    monkeysession.setattr(sys, 'flags', Flags())
+
+    builtins.EncodingWarning = type('EncodingWarning', (Warning,), {})

tests/test_zipp.py

@@ -187,7 +187,7 @@ def test_open_encoding_errors(self):
                 f.read()
 
     @unittest.skipIf(
-        not sys.flags.warn_default_encoding,
+        not getattr(sys.flags, 'warn_default_encoding', 0),
         "Requires warn_default_encoding",
     )
     @pass_alpharep