docs: def command(cmd):
      """Execute command and raise an exception upon an error.
  
        >>> 'README' in command('ls')
        True
        >>> command('nonexistingcommand')  #doctest: +ELLIPSIS
        Traceback (most recent call last):
        ...
        SdistCreationError
  
      """
      status, out = commands.getstatusoutput(cmd)
      if status is not 0:
          logger.error("Something went wrong:")
          logger.error(out)
          raise SdistCreationError()
      return out