Fix invalid importing of importlib.reader in Python 3.9

Fix pytest-dev#9608

Author: nicoddemus

changelog/9608.bugfix.rst

@@ -0,0 +1 @@
+Fix invalid importing of ``importlib.reader`` in Python 3.9.

src/_pytest/assertion/rewrite.py

@@ -44,6 +44,8 @@
 if TYPE_CHECKING:
     from _pytest.assertion import AssertionState
 
+if sys.version_info >= (3, 10):
+    from importlib.readers import FileReader
 
 assertstate_key = StashKey["AssertionState"]()
 
@@ -276,10 +278,7 @@ def get_data(self, pathname: Union[str, bytes]) -> bytes:
     if sys.version_info >= (3, 10):
 
         def get_resource_reader(self, name: str) -> importlib.abc.TraversableResources:  # type: ignore
-            from types import SimpleNamespace
-            from importlib.readers import FileReader
-
-            return FileReader(SimpleNamespace(path=self._rewritten_names[name]))
+            return FileReader(types.SimpleNamespace(path=self._rewritten_names[name]))
 
 
 def _write_pyc_fp(