Fixed to split Authorization header only once:

To avoid IndexError

Author: hirokiky

oauth2_provider/oauth2_validators.py

@@ -35,7 +35,7 @@ def _extract_basic_auth(self, request):
         if not auth:
             return None
 
-        auth_type, auth_string = auth.split(' ')
+        auth_type, auth_string = auth.split(' ', 1)
         if auth_type != "Basic":
             return None