Update Redis exception to drop stack trace

Full stack trace is probably not needed as the Redis data corruption is probably happening somewhere else, the error log should make it easier to investigate it when it does happen.

ckanext/harvest/queue.py

@@ -212,11 +212,9 @@ class RedisConsumer(object):
         while True:
             key, body = self.redis.blpop(self.routing_key)
             try:
-                self.redis.set(self.persistance_key(body),
-                            str(datetime.datetime.now()))
-            except Exception:
-                import traceback
-                log.error("Redis Exception: %s %s", traceback.format_stack(), traceback.format_exc())
+                self.redis.set(self.persistance_key(body), str(datetime.datetime.now()))
+            except Exception as e:
+                log.error("Redis Exception: %s", e)
                 continue
 
             yield (FakeMethod(body), self, body)

ckanext/harvest/tests/test_queue.py

@@ -344,7 +344,7 @@ class TestHarvestCorruptRedis(object):
 
             assert mock_log_error.call_count == 1
             args, _ = mock_log_error.call_args_list[0]
-            assert "TypeError: cannot concatenate 'str' and 'NoneType' objects" in args[2]
+            assert "cannot concatenate 'str' and 'NoneType' objects" in args[1]
 
         finally:
             redis.delete('ckanext-harvest:some-random-key-2')