When implementing the "-X dev" mode, Victor was asked to make it behave differently from "-Wd", such that "python -bb -X dev" would still raise errors for bytes comparisons.

I don't think making "-X dev" and "-Wd" inconsistent with each other is the right way to address that request. Instead, I think we should find a way to make "-bb" *always* take precedence over any supplied "-W" options.

One way to do that would be to adopt an approach similar to what I've proposed for "-X dev" in https://bugs.python.org/issue32230: instead of making the warnings module aware of the "-bb" setting, we'd instead adjust the initialisation code to inject "error::BytesWarning" into sys.warnoptions *after* all of the entries from environment variables and the command line.