Run a command and return stdout.

  Would be better to use subprocess.check_output, but this works on 2.6,
  which is still the system Python on CentOS 7.

def system_call(command):
  """Run a command and return stdout.

  Would be better to use subprocess.check_output, but this works on 2.6,
  which is still the system Python on CentOS 7."""
  p = subprocess.Popen([command], stdout=subprocess.PIPE, shell=True)
  return p.stdout.read()