Fix auth parsing for proxies

Co-authored-by: adamp01 <@adamp01>

requests/utils.py

@@ -974,6 +974,10 @@ def prepend_scheme_if_needed(url, new_scheme):
     if not netloc:
         netloc, path = path, netloc
 
+    if auth:
+        # parse_url doesn't provide the netloc with auth
+        # so we'll add it ourselves.
+        netloc = '@'.join([auth, netloc])
     if scheme is None:
         scheme = new_scheme
     if path is None:

tests/test_utils.py

@@ -602,6 +602,14 @@ def test_parse_header_links(value, expected):
         ('example.com/path', 'http://example.com/path'),
         ('//example.com/path', 'http://example.com/path'),
         ('example.com:80', 'http://example.com:80'),
+        (
+            'http://user:pass@example.com/path?query',
+            'http://user:pass@example.com/path?query'
+        ),
+        (
+            'http://user@example.com/path?query',
+            'http://user@example.com/path?query'
+        )
     ))
 def test_prepend_scheme_if_needed(value, expected):
     assert prepend_scheme_if_needed(value, 'http') == expected