new_contents: from fabric.api import sudo, hide
  
  from patchwork.files import append
  
  
  def _keyfile(who):
      return "/home/%s/.ssh/authorized_keys" % who
  
  
  def copy_pubkey(from_, to):
      """
      Copy remote user ``from_``'s authorized keys to user ``to``.
  
      I.e. allow ``from_`` to SSH into the server as ``to``.
      """
      with hide('stdout'):
          append(
              filename=_keyfile(to),
              # Leading newline to ensure keys stay separate
              text=['\n'] + sudo("cat %s" % _keyfile(from_)).splitlines(),
              runner=sudo
          )
  
subject: Add pubkey copy method