Required by who though? If your business etc depends upon some code, it's up to you to ensure its quality, surely? You copy some code onto your machine then it's your codebase, right?
While I think anyone unwilling to sign their code is negligent, I also feel anyone unwilling to ensure credible review of code has been done before pushing it to production is equally negligent.
While I think anyone unwilling to sign their code is negligent, I also feel anyone unwilling to ensure credible review of code has been done before pushing it to production is equally negligent.