Is it possible for rubygems to reject unsigned releases?

[Kris Leech]

I want to release signed releases only.

I use `signing_key` and `cert_chain` in gemspec but I have to make these conditional on the key existing otherwise, in Gemfile, `gem 'my_gem', path: '~/dev/my_gem'` fails.

Sometimes I release from a computer without the key and I end up accidentally pushing an unsigned gem.

Does anyone have a way of handling this?

Thanks!