title: TeamCity agent error "failed to perform checkout on agent"
body: <p>I am running my TeamCity 7 server and agent on MacOS. My repo is on github. I use ssh and I know that the authentication is correctly configured, because the test is successful. </p>
  
  <p>The build works fine when I use VCS Checkout Mode "Automatically on server", however when I use VCS Checkout mode "Automatically on agent" I get this error.</p>
  
  <pre><code>[13:40:35][Updating sources] Failed to perform checkout on agent: '/usr/bin/git fetch --progress origin +refs/heads/master:refs/remotes/origin/master' command failed.
  stderr: java.io.IOException: Authentication failed
      at org.jetbrains.git4idea.ssh.SSHMain.authenticate(SSHMain.java:275)
      at org.jetbrains.git4idea.ssh.SSHMain.start(SSHMain.java:159)
      at org.jetbrains.git4idea.ssh.SSHMain.main(SSHMain.java:139)
  fatal: The remote end hung up unexpectedly
  </code></pre>
  
  <p>What am I missing?</p>