Reraise sensible errors from auto_chmod

Author: Avasam

Diff for: newsfragments/4593.feature.rst

@@ -0,0 +1 @@
+Reraise error from ``setuptools.command.easy_install.auto_chmod`` instead of nonsensical ``TypeError: 'Exception' object is not subscriptable`` -- by :user:`Avasam`

Diff for: setuptools/command/easy_install.py

@@ -34,7 +34,7 @@
 from collections.abc import Iterable
 from glob import glob
 from sysconfig import get_path
-from typing import TYPE_CHECKING
+from typing import TYPE_CHECKING, Callable, TypeVar
 
 from jaraco.text import yield_lines
 
@@ -89,6 +89,8 @@
     'get_exe_prefixes',
 ]
 
+_T = TypeVar("_T")
+
 
 def is_64bit():
     return struct.calcsize("P") == 8
@@ -1786,13 +1788,14 @@ def _first_line_re():
     return re.compile(first_line_re.pattern.decode())
 
 
-def auto_chmod(func, arg, exc):
+# Must match shutil._OnExcCallback
+def auto_chmod(func: Callable[..., _T], arg: str, exc: BaseException) -> _T:
+    """shutils onexc callback to automatically call chmod for certain functions."""
+    # Only retry for scenarios known to have an issue
     if func in [os.unlink, os.remove] and os.name == 'nt':
         chmod(arg, stat.S_IWRITE)
         return func(arg)
-    et, ev, _ = sys.exc_info()
-    # TODO: This code doesn't make sense. What is it trying to do?
-    raise (ev[0], ev[1] + (" %s %s" % (func, arg)))  # pyright: ignore[reportOptionalSubscript, reportIndexIssue]
+    raise exc
 
 
 def update_dist_caches(dist_path, fix_zipimporter_caches):