code: def _apply_common_rules(self, part, maxlength):
          
          part = part.strip()
          
          if self.fix:
              part = part.strip('.')
          
          if not part:
              return part, 'It cannot be empty.'
          
          if len(part) > maxlength:
              return part, 'It cannot be longer than %i chars.' % maxlength
          
          if part[0] == '.':
              return part, 'It cannot start with a dot.'
          
          if part[-1] == '.':
              return part, 'It cannot end with a dot.'
          
          if '..' in part:
              return part, 'It cannot contain consecutive dots.'
          
          return part, ''
docs: This method contains the rules that must be applied to both the
          domain and the local part of the e-mail address.