Update __init__.py

hmac.new expects key to be a bytearray

Author: jaitaiwan

oauth2/__init__.py

@@ -903,7 +903,7 @@ def sign(self, request, consumer, token):
         """Builds the base signature string."""
         key, raw = self.signing_base(request, consumer, token)
 
-        hashed = hmac.new(key, raw, sha)
+        hashed = hmac.new(key.encode('bytearray'), raw, sha)
 
         # Calculate the digest base 64.
         return binascii.b2a_base64(hashed.digest())[:-1]