Prevent a TypeError in compat.py311.shutil_rmtree (#4382)

Author: abravalheri

newsfragments/4382.bugfix.rst

@@ -0,0 +1 @@
+Prevent a ``TypeError: 'NoneType' object is not callable`` when ``shutil_rmtree`` is called without an ``onexc`` parameter on Python<=3.11 -- by :user:`Avasam`

setuptools/compat/py311.py

@@ -1,12 +1,26 @@
-import sys
+from __future__ import annotations
+
 import shutil
+import sys
+from typing import Any, Callable, TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from _typeshed import StrOrBytesPath, ExcInfo
+
+# Same as shutil._OnExcCallback from typeshed
+_OnExcCallback = Callable[[Callable[..., Any], str, BaseException], object]
 
 
-def shutil_rmtree(path, ignore_errors=False, onexc=None):
+def shutil_rmtree(
+    path: StrOrBytesPath,
+    ignore_errors: bool = False,
+    onexc: _OnExcCallback | None = None,
+) -> None:
     if sys.version_info >= (3, 12):
         return shutil.rmtree(path, ignore_errors, onexc=onexc)
 
-    def _handler(fn, path, excinfo):
-        return onexc(fn, path, excinfo[1])
+    def _handler(fn: Callable[..., Any], path: str, excinfo: ExcInfo) -> None:
+        if onexc:
+            onexc(fn, path, excinfo[1])
 
     return shutil.rmtree(path, ignore_errors, onerror=_handler)