Run a command in a shell.

def ExecuteCmd(cmd, quiet=False):
  """ Run a command in a shell. """
  result = None
  if quiet:
    with open(os.devnull, "w") as fnull:
      result = subprocess.call(cmd, shell=True, stdout=fnull, stderr=fnull)
  else:
    result = subprocess.call(cmd, shell=True)
  return result