Export with_failure_handling

lib/rollbot/command/__init__.py

@@ -1,2 +1,3 @@
 from .decorators import as_command, on_startup, on_shutdown, get_command_config
-from .injection import Args, ArgList, ArgListSplitOn, ArgParse, Database, Lazy
+from .failure import RollbotFailure, with_failure_handling
+from .injection import Args, ArgList, ArgListSplitOn, ArgParse, Database, Lazy