In rmtree, have onerror catch only PermissionError

The onerror function is still called on, and tries to resolve, any
exception. But now, when it re-calls the file deletion function
passed as func, the only exception it catches to conditionally
convert to SkipTest is PermissionError (or derived exceptions).

The old behavior of catching Exception was overly broad, and
inconsistent with the hard-coded prefix of "FIXME: fails with:
PermissionError" used to build the SkipTest exception messages.

This commit also changes the message to use an f-string (which was
one of the styles in the equivalent but differently coded duplicate
logic eliminated in 5039df3, and seems clearer in this case). That
change is a pure refactoring, not affecting generated messages.

Author: EliahKagan

git/util.py

@@ -188,11 +188,11 @@ def onerror(func: Callable, path: PathLike, exc_info: str) -> None:
 
         try:
             func(path)  # Will scream if still not possible to delete.
-        except Exception as ex:
+        except PermissionError as ex:
             if HIDE_WINDOWS_KNOWN_ERRORS:
                 from unittest import SkipTest
 
-                raise SkipTest("FIXME: fails with: PermissionError\n  {}".format(ex)) from ex
+                raise SkipTest(f"FIXME: fails with: PermissionError\n  {ex}") from ex
             raise
 
     return shutil.rmtree(path, False, onerror)