docs: def add_configuration_file(self, file_name):
          '''Register a file path from which to read parameter values.
  
          This method can be called multiple times to register multiple files for
          querying.  Files are expected to be ``ini`` formatted.
  
          No assumptions should be made about the order that the registered files
          are read and values defined in multiple files may have unpredictable
          results.
  
          **Arguments**
  
          :``file_name``: Name of the file to add to the parameter search.
  
          '''
  
          logger.info('adding %s to configuration files', file_name)
  
          if file_name not in self.configuration_files and self._inotify:
              self._watch_manager.add_watch(file_name, pyinotify.IN_MODIFY)
  
          if os.access(file_name, os.R_OK):
              self.configuration_files[file_name] = SafeConfigParser()
              self.configuration_files[file_name].read(file_name)
          else:
              logger.warn('could not read %s', file_name)
              warnings.warn('could not read {}'.format(file_name), ResourceWarning)