Fix request_force_stop_sigrtmin failing for python3

request_force_stop_sigrtmin would fail for python3 because it would
try to read frame attributes that have been removed in python3

This patch fixes that by reading more fram attributes only for
python2

rq/worker.py

@@ -734,8 +734,12 @@ class HerokuWorker(Worker):
     causes the horse to crash `imminent_shutdown_delay` seconds later
     """
     imminent_shutdown_delay = 6
-    frame_properties = ['f_code', 'f_exc_traceback', 'f_exc_type', 'f_exc_value',
-                        'f_lasti', 'f_lineno', 'f_locals', 'f_restricted', 'f_trace']
+
+    frame_properties = ['f_code', 'f_lasti', 'f_lineno', 'f_locals', 'f_trace']
+    if sys.version_info[:2] <= (3, 0):
+        frame_properties.extend(
+            ['f_exc_traceback', 'f_exc_type', 'f_exc_value', 'f_restricted']
+        )
 
     def setup_work_horse_signals(self):
         """Modified to ignore SIGINT and SIGTERM and only handle SIGRTMIN"""
@@ -753,10 +757,10 @@ class HerokuWorker(Worker):
 
     def request_stop_sigrtmin(self, signum, frame):
         if self.imminent_shutdown_delay == 0:
-            logger.warn('Imminent shutdown, raising ShutDownImminentException immediately')
+            self.log.warning('Imminent shutdown, raising ShutDownImminentException immediately')
             self.request_force_stop_sigrtmin(signum, frame)
         else:
-            logger.warn('Imminent shutdown, raising ShutDownImminentException in %d seconds',
+            self.log.warning('Imminent shutdown, raising ShutDownImminentException in %d seconds',
                         self.imminent_shutdown_delay)
             signal.signal(signal.SIGRTMIN, self.request_force_stop_sigrtmin)
             signal.signal(signal.SIGALRM, self.request_force_stop_sigrtmin)
@@ -764,5 +768,5 @@ class HerokuWorker(Worker):
 
     def request_force_stop_sigrtmin(self, signum, frame):
         info = dict((attr, getattr(frame, attr)) for attr in self.frame_properties)
-        logger.warn('raising ShutDownImminentException to cancel job...')
+        self.log.warning('raising ShutDownImminentException to cancel job...')
         raise ShutDownImminentException('shut down imminent (signal: %s)' % signal_name(signum), info)