Convert os.altsep to '/' in filenames when creating ZipInfo objects

This causes the zipfile module to also consider the character defined by
`os.altsep` (if there is one) to be a path separator and convert it to a
forward slash, as defined by the zip specification.

Author: pR0Ps

Lib/zipfile/__init__.py

@@ -352,6 +352,8 @@ def _sanitize_filename(filename):
     # ZIP format specification.
     if os.sep != "/" and os.sep in filename:
         filename = filename.replace(os.sep, "/")
+    if os.altsep and os.altsep != "/" and os.altsep in filename:
+        filename = filename.replace(os.altsep, "/")
     return filename
 
 

Misc/NEWS.d/next/Library/2022-05-02-16-21-05.gh-issue-92184.hneGVW.rst

@@ -0,0 +1,2 @@
+When creating zip files using the ``zipfile`` module, ``os.altsep`` will always
+be treated as a path separator. Patch by Carey Metcalfe.