Fix access token retrieval message

The metadata refresh command should log the short code of the partner for which an access token is being retrieved instead of always logging the value of the partner_code argument.

course_discovery/apps/course_metadata/management/commands/refresh_course_metadata.py

@@ -85,7 +85,7 @@ class Command(BaseCommand):
 
         token_type = 'JWT'
         for partner in partners:
-            logger.info('Retrieving access token for partner [{}]'.format(partner_code))
+            logger.info('Retrieving access token for partner [{}]'.format(partner.short_code))
 
             try:
                 access_token, __ = EdxRestApiClient.get_oauth_access_token(