Replace bare except with AttributeError

luigi/contrib/docker_runner.py

@@ -227,7 +227,7 @@ def run(self):
                 container_name = self.name
             try:
                 message = e.message
-            except:
+            except AttributeError:
                 message = str(e)
             self.__logger.error("Container " + container_name +
                                 " exited with non zero code: " + message)