Currently if the user specifies a bad GPG location SourceTree won't question it. This is done because we don't want to assume the output from gpg will stay the same, but we should be able to handle failed calls. Currently SourceTree displays the attached image when trying to enable GPG on a repository. Instead, display a message saying GPG couldn't be found at location X with suggestions for fixes and/or a link to the built-in documents which do assist the user.