Change to be specific to urllib

src/_pytest/_code/code.py

@@ -700,10 +700,21 @@ class ExceptionInfo(Generic[E]):
         return fmt.repr_excinfo(self)
 
     def _stringify_exception(self, exc: BaseException) -> str:
+        try:
+            notes = getattr(exc, "__notes__", [])
+        except KeyError:
+            # Workaround for https://github.com/python/cpython/issues/98778 on
+            # Python <= 3.9, and some 3.10 and 3.11 patch versions.
+            HTTPError = getattr(sys.modules.get("urllib.error", None), "HTTPError", ())
+            if sys.version_info[:2] <= (3, 11) and isinstance(exc, HTTPError):
+                notes = []
+            else:
+                raise
+
         return "\n".join(
             [
                 str(exc),
-                *safe_getattr(exc, "__notes__", []),
+                *notes,
             ]
         )
 

testing/acceptance_test.py

@@ -1450,11 +1450,3 @@ def test_issue_9765(pytester: Pytester) -> None:
         raise AssertionError(
             f"pytest command failed:\n{exc.stdout=!s}\n{exc.stderr=!s}"
         ) from exc
-
-
-def test_issue_11872() -> None:
-    # see https://github.com/pytest-dev/pytest/issues/11872
-    from urllib.error import HTTPError
-
-    with pytest.raises(HTTPError, match="Not Found"):
-        raise HTTPError(code=404, msg="Not Found", fp=None, hdrs=None, url="")  # type: ignore [arg-type]

testing/python/raises.py

@@ -302,3 +302,16 @@ class TestRaises:
             with pytest.raises(("hello", NotAnException)):  # type: ignore[arg-type]
                 pass  # pragma: no cover
         assert "must be a BaseException type, not str" in str(excinfo.value)
+
+    def test_issue_11872(self) -> None:
+        """Regression test for #11872.
+
+        urllib.error.HTTPError on Python<=3.9 raises KeyError instead of
+        AttributeError on invalid attribute access.
+
+        https://github.com/python/cpython/issues/98778
+        """
+        from urllib.error import HTTPError
+
+        with pytest.raises(HTTPError, match="Not Found"):
+            raise HTTPError(code=404, msg="Not Found", fp=None, hdrs=None, url="")  # type: ignore [arg-type]