docs: def _authenticate_ssh(org):
      """Try authenticating via ssh, if succesful yields a User, otherwise raises Error."""
      # Try to get username from git config
      username = os.environ.get(f"{org.upper()}_USERNAME")
      # Require ssh-agent
      child = pexpect.spawn("ssh -T git@github.com", encoding="utf8")
      # GitHub prints 'Hi {username}!...' when attempting to get shell access
      i = child.expect(["Hi (.+)! You've successfully authenticated",
                        "Enter passphrase for key",
                        "Permission denied",
                        "Are you sure you want to continue connecting"])
      child.close()
  
      if i == 0:
          if username is None:
              username = child.match.groups()[0]
      else:
          return None
  
      return User(name=username,
                  repo=f"git@github.com:{org}/{username}")