fixup: older python support

Author: RonnyPfannschmidt

pyproject.toml

@@ -117,6 +117,7 @@ template = "changelog/_template.rst"
 
 [tool.mypy]
 mypy_path = "src"
+python="3.9"
 check_untyped_defs = true
 # Hopefully we can set this someday!
 # disallow_any_expr = true

src/pluggy/_hook_callers.py

@@ -38,11 +38,16 @@
 
 _T_HookImpl = TypeVar("_T_HookImpl", bound="HookImpl")
 
+
 # Type alias for completion hook functions
-CompletionHook = Callable[
-    [object | list[object] | None, BaseException | None],
-    tuple[object | list[object] | None, BaseException | None],
-]
+class CompletionHook(Protocol):
+    """completion hooks are used to express the teardown of hookwrappers
+    as python has no builtin way to change the result using a
+    """
+
+    def __call__(
+        self, result: object | list[object] | None, exception: BaseException | None
+    ) -> tuple[object | list[object] | None, BaseException | None]: ...
 
 
 def _insert_hookimpl_into_list(