Don't log job exceptions twice (#1746)

* Don't log job exceptions twice

* Preserve traceback while encountering deserialization error

rq/worker.py

@@ -1164,6 +1164,7 @@ class Worker:
 
     def handle_exception(self, job: 'Job', *exc_info):
         """Walks the exception handler stack to delegate exception handling."""
+
         exc_string = ''.join(traceback.format_exception(*exc_info))
 
         # If the job cannot be deserialized, it will raise when func_name or
@@ -1175,14 +1176,17 @@ class Worker:
                 'arguments': job.args,
                 'kwargs': job.kwargs,
             }
+            func_name = job.func_name
         except DeserializationError:
             extra = {}
+            func_name = '<DeserializationError>'
 
         # the properties below should be safe however
         extra.update({'queue': job.origin, 'job_id': job.id})
         
         # func_name
-        self.log.error(exc_string, exc_info=True, extra=extra)
+        self.log.error(f'[Job {job.id}]: exception raised while executing ({func_name})\n' + exc_string,
+                       extra=extra)
 
         for handler in self._exc_handlers:
             self.log.debug('Invoking exception handler %s', handler)