Fixed an issue where `birth` not present in Redis (#901)

* Fixed an issue where `birth` not present in Redis

Fixed an issue where worker.refresh() may fail if `birth` is not present in Redis

* added test coverage

rq/worker.py

@@ -544,7 +544,10 @@ class Worker(object):
             self.last_heartbeat = utcparse(as_text(last_heartbeat))
         else:
             self.last_heartbeat = None
+        if birth:
             self.birth_date = utcparse(as_text(birth))
+        else:
+            self.birth_date = None
         if failed_job_count:
             self.failed_job_count = int(as_text(failed_job_count))
         if successful_job_count:

tests/test_worker.py

@@ -202,8 +202,9 @@ class TestWorker(RQTestCase):
         q = Queue()
         w = Worker([q])
         w.register_birth()
+        birth = self.testconn.hget(w.key, 'birth')
         last_heartbeat = self.testconn.hget(w.key, 'last_heartbeat')
-
+        self.assertTrue(birth is not None)
         self.assertTrue(last_heartbeat is not None)
         w = Worker.find_by_key(w.key)
         self.assertIsInstance(w.last_heartbeat, datetime)
@@ -212,6 +213,10 @@ class TestWorker(RQTestCase):
         # for compatibility reasons
         self.testconn.hdel(w.key, 'last_heartbeat')
         w.refresh()
+        # worker.refresh() shouldn't fail if birth is None
+        # for compatibility reasons
+        self.testconn.hdel(w.key, 'birth')
+        w.refresh()
 
     def test_work_fails(self):
         """Failing jobs are put on the failed queue."""