[3.12] GH-85168: Use filesystem encoding when converting to/from file URIs (GH-126852) (#127040)

GH-85168: Use filesystem encoding when converting to/from `file` URIs (GH-126852)

Adjust `urllib.request.url2pathname()` and `pathname2url()` to use the
filesystem encoding when quoting and unquoting file URIs, rather than
forcing use of UTF-8.

No changes are needed in the `nturl2path` module because Windows always
uses UTF-8, per PEP 529.
(cherry picked from commit c9b399fbdb)

Co-authored-by: Barney Gale <barney.gale@gmail.com>

Lib/urllib/request.py

@@ -1685,12 +1685,16 @@ else:
             # URL has an empty authority section, so the path begins on the
             # third character.
             pathname = pathname[2:]
-        return unquote(pathname)
+        encoding = sys.getfilesystemencoding()
+        errors = sys.getfilesystemencodeerrors()
+        return unquote(pathname, encoding=encoding, errors=errors)
 
     def pathname2url(pathname):
         """OS-specific conversion from a file system path to a relative URL
         of the 'file' scheme; not recommended for general use."""
-        return quote(pathname)
+        encoding = sys.getfilesystemencoding()
+        errors = sys.getfilesystemencodeerrors()
+        return quote(pathname, encoding=encoding, errors=errors)
 
 
 ftpcache = {}