docs: def patch_file_open(): # pragma: no cover
      """A Monkey patch to log opening and closing of files, which is useful for
      debugging file descriptor exhaustion."""
  
      openfiles = set()
      oldfile = builtins.file
  
      class newfile(oldfile):
          def __init__(self, *args, **kwargs):
              self.x = args[0]
  
              all_fds = count_open_fds()
  
              print('### {} OPENING {} ( {} total )###'.format(
                  len(openfiles), str(self.x), all_fds))
              oldfile.__init__(self, *args, **kwargs)
  
              openfiles.add(self)
  
          def close(self):
              print('### {} CLOSING {} ###'.format(len(openfiles), str(self.x)))
              oldfile.close(self)
              openfiles.remove(self)
  
      def newopen(*args, **kwargs):
          return newfile(*args, **kwargs)
  
      builtins.file = newfile
      builtins.open = newopen