message: test: make sure to close files
diff: @@ -24,7 +24,8 @@ def memory():
  def add_file(fs, filename=FILENAME):
  - copyfileobj((Path(__file__).parent / 'data' / filename).open('rb'), fs.open(filename, 'wb'))
  + with (Path(__file__).parent / 'data' / filename).open('rb') as source, fs.open(filename, 'wb') as dest:
  + copyfileobj(source, dest)
  class TestPythonFilesystem:
  