<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def com_daltonmaag_check_ufolint(font):
 """Run ufolint on UFO source directory."""

  import subprocess
  ufolint_cmd = ["ufolint", font]

  try:
    subprocess.check_output(ufolint_cmd, stderr=subprocess.STDOUT)
  except subprocess.CalledProcessError as e:
    yield FAIL, ("ufolint failed the UFO source. Output follows :"
                 "\n\n{}\n").format(e.output.decode())
  except OSError:
    yield ERROR, "ufolint is not available!"
  else:
    yield PASS, "ufolint passed the UFO source."