<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:

def execute(cmd):
  ''' Call cmd and return output. return None if any exception occurs '''
  try:
    return safely_decode(check_output(cmd))
  except Exception as e:
    logger.warn(u'Couldnt execute cmd: %s.\nReason: %s' % (cmd, e))
    return None