title: ssh key fingerprint error when trying to switch heroku accounts
body: <p>i often need to switch heroku accounts and use a script which does the following:</p>
  
  <pre><code>heroku keys:clear &amp;&amp; rm ~/.heroku/credentials &amp;&amp; heroku list
  </code></pre>
  
  <p>after which i need to enter my credentials for the account i want to switch to:</p>
  
  <pre><code>Enter your Heroku credentials.
  Email: fake@gmail.com
  Password: 
  Uploading ssh public key /Users/fake/.ssh/id_rsa.pub
  !   Fingerprint already exists. Please use one ssh key per Heroku account
  </code></pre>
  
  <p>unfortunatelly i can´t get passed this error.</p>
  
  <p>any help much appreciated.</p>