diff --git a/rhodecode/lib/celerylib/utils.py b/rhodecode/lib/celerylib/utils.py
--- a/rhodecode/lib/celerylib/utils.py
+++ b/rhodecode/lib/celerylib/utils.py
@@ -54,9 +54,7 @@ def safe_json(get, section, key):
         value = get(key)
         json_value = json.loads(value)
     except ValueError:
-        msg = 'The %s=%s is not valid json in section %s' % (
-            key, value, section
-        )
+        msg = f'The {key}={value} is not valid json in section {section}'
         raise ValueError(msg)
 
     return json_value
@@ -71,11 +69,7 @@ def raw_2_schedule(schedule_value, sched
     scheduler_cls = schedule_type_map.get(schedule_type)
 
     if scheduler_cls is None:
-        raise ValueError(
-            'schedule type %s in section is invalid' % (
-                schedule_type,
-            )
-        )
+        raise ValueError(f'schedule type {schedule_type} in section is invalid')
     try:
         schedule = scheduler_cls(schedule_value)
     except TypeError:
diff --git a/rhodecode/model/db.py b/rhodecode/model/db.py
--- a/rhodecode/model/db.py
+++ b/rhodecode/model/db.py
@@ -5290,8 +5290,11 @@ class ScheduleEntry(Base, BaseModel):
         UniqueConstraint('task_uid', name='s_task_uid_idx'),
         base_table_args,
     )
-
-    schedule_types = ['crontab', 'timedelta', 'integer']
+    SCHEDULE_TYPE_INTEGER = "integer"
+    SCHEDULE_TYPE_CRONTAB = "crontab"
+    SCHEDULE_TYPE_TIMEDELTA = "timedelta"
+
+    schedule_types = [SCHEDULE_TYPE_CRONTAB, SCHEDULE_TYPE_TIMEDELTA, SCHEDULE_TYPE_INTEGER]
     schedule_entry_id = Column('schedule_entry_id', Integer(), primary_key=True)
 
     schedule_name = Column("schedule_name", String(255), nullable=False, unique=None, default=None)