Split execute job to expose issue 702

In order to create a test for issue 702 we had to split execute_job
to a fork_work_horse function and a monitor_work_horse function.

rq/worker.py

@@ -503,13 +503,9 @@ class Worker(object):
         self.log.debug('Sent heartbeat to prevent worker timeout. '
                        'Next one should arrive within {0} seconds.'.format(timeout))
 
-    def execute_job(self, job, queue):
+    def fork_work_horse(self, job, queue):
         """Spawns a work horse to perform the actual work and passes it a job.
-        The worker will wait for the work horse and make sure it executes
-        within the given timeout bounds, or will end the work horse with
-        SIGALRM.
         """
-        self.set_state('busy')
         child_pid = os.fork()
         os.environ['RQ_WORKER_ID'] = self.name
         os.environ['RQ_JOB_ID'] = job.id
@@ -518,20 +514,36 @@ class Worker(object):
         else:
             self._horse_pid = child_pid
             self.procline('Forked {0} at {1}'.format(child_pid, time.time()))
-            while True:
-                try:
-                    os.waitpid(child_pid, 0)
-                    self.set_state('idle')
-                    break
-                except OSError as e:
-                    # In case we encountered an OSError due to EINTR (which is
-                    # caused by a SIGINT or SIGTERM signal during
-                    # os.waitpid()), we simply ignore it and enter the next
-                    # iteration of the loop, waiting for the child to end.  In
-                    # any other case, this is some other unexpected OS error,
-                    # which we don't want to catch, so we re-raise those ones.
-                    if e.errno != errno.EINTR:
-                        raise
+
+    def monitor_work_horse(self, job):
+        """The worker will wait for the work horse and make sure it executes
+        within the given timeout bounds, or will end the work horse with
+        SIGALRM.
+        """
+        while True:
+            try:
+                _, ret_val = os.waitpid(self._horse_pid, 0)
+                break
+            except OSError as e:
+                # In case we encountered an OSError due to EINTR (which is
+                # caused by a SIGINT or SIGTERM signal during
+                # os.waitpid()), we simply ignore it and enter the next
+                # iteration of the loop, waiting for the child to end.  In
+                # any other case, this is some other unexpected OS error,
+                # which we don't want to catch, so we re-raise those ones.
+                if e.errno != errno.EINTR:
+                    raise
+
+    def execute_job(self, job, queue):
+        """Spawns a work horse to perform the actual work and passes it a job.
+        The worker will wait for the work horse and make sure it executes
+        within the given timeout bounds, or will end the work horse with
+        SIGALRM.
+        """
+        self.set_state('busy')
+        self.fork_work_horse(job, queue)
+        self.monitor_work_horse(job)
+        self.set_state('idle')
 
     def main_work_horse(self, job, queue):
         """This is the entry point of the newly spawned work horse."""