Preserve percent-encoded forward slashes.

Lib/nturl2path.py

@@ -24,13 +24,13 @@ def url2pathname(url):
             # convert this to \\host\path\on\remote\host
             # (notice halving of slashes at the start of the path)
             url = url[2:]
-        return urllib.parse.unquote(url).replace('/', '\\')
+        return urllib.parse.unquote(url.replace('/', '\\'))
     comp = url.split('|')
     if len(comp) != 2 or comp[0][-1] not in string.ascii_letters:
         error = 'Bad URL: ' + url
         raise OSError(error)
     drive = comp[0][-1].upper()
-    tail = urllib.parse.unquote(comp[1]).replace('/', '\\')
+    tail = urllib.parse.unquote(comp[1].replace('/', '\\'))
     return drive + ':' + tail
 
 def pathname2url(p):

Lib/test/test_urllib.py

@@ -1587,6 +1587,9 @@ def test_url2pathname_win(self):
         # Localhost paths
         self.assertEqual(fn('//localhost/C:/path/to/file'), 'C:\\path\\to\\file')
         self.assertEqual(fn('//localhost/C|/path/to/file'), 'C:\\path\\to\\file')
+        # Percent-encoded forward slashes are preserved for backwards compatibility
+        self.assertEqual(fn('C:/foo%2fbar'), 'C:\\foo/bar')
+        self.assertEqual(fn('//server/share/foo%2fbar'), '\\\\server\\share\\foo/bar')
         # Round-tripping
         paths = ['C:',
                  r'\\\C\test\\',