When adding used SSH keys to your Bitbucket account, The error displays "Someone has already registered this as a deploy key." however isn't informative on where is the SSH key being used at.
Users then have to run git commands to identify where was the SSH key used.
ssh email@example.com PTY allocation request failed on channel 0 authenticated via a deploy key. You can use git or hg to connect to Bitbucket. Shell access is disabled. This deploy key has read access to the following repositories: username/repo_slug: repo_slug access key label -- name Connection to bitbucket.org closed.
It'd be great if we can display the where is the SSH key is being used on the page so that users don't have to troubleshoot much.