bpo-32498: urllib.parse.unquote also accepts bytes (GH-7768)

diff --git a/Lib/urllib/parse.py b/Lib/urllib/parse.py
index b660878..3a38dc1 100644
--- a/Lib/urllib/parse.py
+++ b/Lib/urllib/parse.py
@@ -631,6 +631,8 @@
 
     unquote('abc%20def') -> 'abc def'.
     """
+    if isinstance(string, bytes):
+        return unquote_to_bytes(string).decode(encoding, errors)
     if '%' not in string:
         string.split
         return string