docs: def _sibpath(path, sibling):
      """
      Return the path to a sibling of a file in the filesystem.
  
      This is useful in conjunction with the special C{__file__} attribute
      that Python provides for modules, so modules can load associated
      resource files.
  
      (Stolen from twisted.python.util)
      """
      return os.path.join(os.path.dirname(os.path.abspath(path)), sibling)