fixed pytest 4 deprecation warning (#5097)

* fixed pytest deprecation warning

* fixed flake8 error

celery/beat.py

@@ -257,7 +257,7 @@ class Scheduler(object):
         adjust = self.adjust
 
         as_now = entry.default_now()
-                         
+
         return (mktime(as_now.timetuple()) +
                 as_now.microsecond / 1e6 +
                 (adjust(next_time_to_run) or 0))

celery/contrib/pytest.py

@@ -51,7 +51,7 @@ def celery_session_app(request,
                        use_celery_app_trap):
     # type: (Any) -> Celery
     """Session Fixture: Return app for session fixtures."""
-    mark = request.node.get_marker('celery')
+    mark = request.node.get_closest_marker('celery')
     config = dict(celery_config, **mark.kwargs if mark else {})
     with _create_app(enable_logging=celery_enable_logging,
                      use_trap=use_celery_app_trap,
@@ -151,7 +151,7 @@ def celery_app(request,
                celery_enable_logging,
                use_celery_app_trap):
     """Fixture creating a Celery application instance."""
-    mark = request.node.get_marker('celery')
+    mark = request.node.get_closest_marker('celery')
     config = dict(celery_config, **mark.kwargs if mark else {})
     with _create_app(enable_logging=celery_enable_logging,
                      use_trap=use_celery_app_trap,