docs: def _backup_file(path):
      """
      Backup a file but never overwrite an existing backup file
      """
      backup_base = '/var/local/woven-backup'
      backup_path = ''.join([backup_base,path])
      if not exists(backup_path):
          directory = ''.join([backup_base,os.path.split(path)[0]])
          sudo('mkdir -p %s'% directory)
          sudo('cp %s %s'% (path,backup_path))