pass exc_string as an argument to log (#1934)

* pass exc_string as an argument to log

* fix test of exception log by accessing right arg

* fix black "error"

rq/worker.py

@@ -1498,7 +1498,9 @@ class Worker(BaseWorker):
         extra.update({'queue': job.origin, 'job_id': job.id})
 
         # func_name
-        self.log.error('[Job %s]: exception raised while executing (%s)\n' + exc_string, job.id, func_name, extra=extra)
+        self.log.error(
+            '[Job %s]: exception raised while executing (%s)\n%s', job.id, func_name, exc_string, extra=extra
+        )
 
         for handler in self._exc_handlers:
             self.log.debug('Invoking exception handler %s', handler)

tests/test_worker.py

@@ -268,7 +268,7 @@ class TestWorker(RQTestCase):
         w.perform_job(job, queue)
 
         # An exception should be logged here at ERROR level
-        self.assertIn("Traceback", mock_logger_error.call_args[0][0])
+        self.assertIn("Traceback", mock_logger_error.call_args[0][3])
 
     def test_heartbeat(self):
         """Heartbeat saves last_heartbeat"""