Oh, my mistake ; I though send_error was to be used internally only, but it's actually a documented public method, that does not enforce to only use "actual" HTTP error code (I wonder what's the point of calling send_error with a non-error status code but that's beyond the point of this bug).

I will finish the work of SpaceOne : do a clean patch with just the modification (no rename of the variable nor comments) and write a test case.