Let cleanup_ghosts accept conn argument

rq/contrib/legacy.py

@@ -11,7 +11,7 @@ from rq import Worker
 logger = logging.getLogger(__name__)
 
 
-def cleanup_ghosts():
+def cleanup_ghosts(conn=None):
     """
     RQ versions < 0.3.6 suffered from a race condition where workers, when
     abruptly terminated, did not have a chance to clean up their worker
@@ -21,8 +21,8 @@ def cleanup_ghosts():
 
     This function will clean up any of such legacy ghosted workers.
     """
-    conn = get_current_connection()
-    for worker in Worker.all():
+    conn = conn if conn else get_current_connection()
+    for worker in Worker.all(connection=conn):
         if conn._ttl(worker.key) == -1:
             ttl = worker.default_worker_ttl
             conn.expire(worker.key, ttl)