Add test for parse_qsl strict_parsing on malformed fields

The strict_parsing=True path in urllib.parse.parse_qsl was only exercised
with empty inputs, which return before the parsing loop, so its ValueError
branch was untested. Add a test that a field without '=' raises ValueError
under strict_parsing (str and bytes) and that well-formed input still parses.

Author: nikolauspschuetz

Lib/test/test_urlparse.py

@@ -1527,6 +1527,15 @@ def test_parse_qsl_false_value(self):
             self.assertEqual(cm.filename, __file__)
             self.assertRaises(ValueError, urllib.parse.parse_qsl, x, separator=1)
 
+    def test_parse_qsl_strict_parsing(self):
+        for func in (urllib.parse.parse_qsl, urllib.parse.parse_qs):
+            self.assertRaises(ValueError, func, 'a=1&b&c=3', strict_parsing=True)
+            self.assertRaises(ValueError, func, b'a=1&b', strict_parsing=True)
+        self.assertEqual(urllib.parse.parse_qsl('a=1&c=3', strict_parsing=True),
+                         [('a', '1'), ('c', '3')])
+        self.assertEqual(urllib.parse.parse_qs('a=1&c=3', strict_parsing=True),
+                         {'a': ['1'], 'c': ['3']})
+
     def test_parse_qsl_errors(self):
         self.assertRaises(TypeError, urllib.parse.parse_qsl, list(b'a=b'))
         self.assertRaises(TypeError, urllib.parse.parse_qsl, iter(b'a=b'))