code: def _import_plugin(module_name, plugin_path, modnames, modlist):
      
      if module_name in modnames:
          return
      try:
          # First add a mock module with the LOCALEPATH attribute so that the
          # helper method can find the locale on import
          mock = _ModuleMock()
          mock.LOCALEPATH = osp.join(plugin_path, module_name, 'locale')
          sys.modules[module_name] = mock
  
          if osp.isdir(osp.join(plugin_path, module_name)):
              module = _import_module_from_path(module_name, plugin_path)
          else:
              module = None
  
          # Then restore the actual loaded module instead of the mock
          if module and getattr(module, 'PLUGIN_CLASS', False):
              sys.modules[module_name] = module
              modlist.append(module)
              modnames.append(module_name)
      except Exception:
          sys.stderr.write("ERROR: 3rd party plugin import failed for "
                           "`{0}`\n".format(module_name))
          traceback.print_exc(file=sys.stderr)
docs: Import the plugin `module_name` from `plugin_path`, add it to `modlist`
      and adds its name to `modnames`.