bpo-42967: coerce bytes separator to string in urllib.parse_qs(l) (GH-24818)

* coerce bytes separator to string

* Add news

* Update Misc/NEWS.d/next/Library/2021-03-11-00-31-41.bpo-42967.2PeQRw.rst
(cherry picked from commit b38601d)

Co-authored-by: Ken Jin <[email protected]>

Author: miss-islington

Lib/test/test_urlparse.py

@@ -893,6 +893,8 @@ def test_parse_qs_separator(self):
             with self.subTest(f"Original: {orig!r}, Expected: {expect!r}"):
                 result = urllib.parse.parse_qs(orig, separator=';')
                 self.assertEqual(result, expect, "Error parsing %r" % orig)
+                result_bytes = urllib.parse.parse_qs(orig, separator=b';')
+                self.assertEqual(result_bytes, expect, "Error parsing %r" % orig)
 
 
     def test_parse_qsl_separator(self):
@@ -912,6 +914,8 @@ def test_parse_qsl_separator(self):
             with self.subTest(f"Original: {orig!r}, Expected: {expect!r}"):
                 result = urllib.parse.parse_qsl(orig, separator=';')
                 self.assertEqual(result, expect, "Error parsing %r" % orig)
+                result_bytes = urllib.parse.parse_qsl(orig, separator=b';')
+                self.assertEqual(result_bytes, expect, "Error parsing %r" % orig)
 
 
     def test_urlencode_sequences(self):

Lib/urllib/parse.py

@@ -733,6 +733,7 @@ def parse_qsl(qs, keep_blank_values=False, strict_parsing=False,
         Returns a list, as G-d intended.
     """
     qs, _coerce_result = _coerce_args(qs)
+    separator, _ = _coerce_args(separator)
 
     if not separator or (not isinstance(separator, (str, bytes))):
         raise ValueError("Separator must be of type string or bytes.")

Misc/NEWS.d/next/Library/2021-03-11-00-31-41.bpo-42967.2PeQRw.rst

@@ -0,0 +1,3 @@
+Allow :class:`bytes` ``separator`` argument in ``urllib.parse.parse_qs`` and
+``urllib.parse.parse_qsl`` when parsing :class:`str` query strings.  Previously,
+this raised a ``TypeError``.