docs: def save(self):
          """ Write the textual content (self._txt) to .spec file (self.fn). """
          if not self.txt:
              # no changes
              return
          if not self.fn:
              raise exception.InvalidAction(
                  "Can't save .spec file without its file name specified.")
          f = codecs.open(self.fn, 'w', encoding='utf-8')
          f.write(self.txt)
          f.close()
          self._rpmspec = None