Fixed wrong keys used to WATCH dependencies (#1605)

This bug has opened a lot of possible race-conditions, since the
watch-logic from redis did not fail anymore, if dependencies have been
changed in parallel.

rq/job.py

@@ -485,7 +485,8 @@ class Job:
         connection = pipeline if pipeline is not None else self.connection
 
         if watch and self._dependency_ids:
-            connection.watch(*self._dependency_ids)
+            connection.watch(*[self.key_for(dependency_id)
+                               for dependency_id in self._dependency_ids])
 
         jobs = [job
                 for job in self.fetch_many(self._dependency_ids, connection=self.connection, serializer=self.serializer)
@@ -970,7 +971,8 @@ class Job:
         connection = pipeline if pipeline is not None else self.connection
 
         if pipeline is not None:
-            connection.watch(*self.dependency_ids)
+            connection.watch(*[self.key_for(dependency_id)
+                               for dependency_id in self._dependency_ids])
 
         dependencies_ids = {_id.decode()
                             for _id in connection.smembers(self.dependencies_key)}

tests/test_job.py

@@ -998,7 +998,7 @@ class TestJob(RQTestCase):
             pipeline.multi()
 
             with self.assertRaises(WatchError):
-                self.testconn.set(dependency_job.id, 'somethingelsehappened')
+                self.testconn.set(Job.key_for(dependency_job.id), 'somethingelsehappened')
                 pipeline.touch(dependency_job.id)
                 pipeline.execute()