added set_single_latch ready for update task transaction. RE. DBOARD3-433

inventory_provider/tasks/common.py

@@ -98,7 +98,7 @@ def update_latch_status(config, pending=False, failure=False):
         if not pending and not failure:
             if not latch['pending'] and not latch['failure']:
                 logger.error(
-                    'updating latch for db {db} with pending=failure=True, '
+                    f'updating latch for db {db} with pending=True, '
                     f'but latch is already {latch}')
             latch['timestamp'] = now
         latch['pending'] = pending
@@ -112,17 +112,21 @@ def set_latch(config, new_current, new_next, timestamp):
         new_current, new_next))
 
     for db in config['redis-databases']:
-        latch = {
-            'current': new_current,
-            'next': new_next,
-            'this': db,
-            'pending': False,
-            'failure': False,
-            'timestamp': timestamp
-        }
-
         r = _get_redis(config, dbid=db)
-        r.set('db:latch', json.dumps(latch))
+        set_single_latch(r, db, new_current, new_next, timestamp)
+
+
+def set_single_latch(r, db, new_current, new_next, timestamp):
+
+    latch = {
+        'current': new_current,
+        'next': new_next,
+        'this': db,
+        'pending': False,
+        'failure': False,
+        'timestamp': timestamp
+    }
+    r.set('db:latch', json.dumps(latch))
 
 
 def latch_db(config):