code: def interface_errors(self):
          
          output = []  # used to store the list of interfaces with errors.
          # get a string of each physical and logical interface element
          dev_response = self._session.command('sh interfaces extensive')
          ints = dev_response.xpath('//physical-interface')
          ints += dev_response.xpath('//logical-interface')
          for i in ints:
              # Grab the interface name for user output.
              int_name = i.xpath('name')[0].text.strip()
              # Only check certain interface types.
              if (('ge' or 'fe' or 'ae' or 'xe' or 'so' or 'et' or 'vlan' or
                   'lo0' or 'irb') in int_name):
                  try:
                      status = (i.xpath('admin-status')[0].text.strip() +
                                '/' + i.xpath('oper-status')[0].text.strip())
                  except IndexError:
                      pass
                  else:
                      for error in self._error_parse(i, "input"):
                          output.append("%s (%s)%s" % (int_name, status,
                                                       error))
                      for error in self._error_parse(i, "output"):
                          output.append("%s (%s)%s" % (int_name, status,
                                                       error))
          if output == []:
              output.append('No interface errors were detected on this device.')
          return '\n'.join(output) + '\n'
docs: Parse 'show interfaces extensive' and return interfaces with errors.
  
          Purpose: This function is called for the -e flag. It will let the user
                 | know if there are any interfaces with errors, and what those
                 | interfaces are.
  
          @returns: The output that should be shown to the user.
          @rtype: str