'Expect written bytes to be a tarball.'

@contextmanager
def writer(self):

    result = BytesIO()
    (yield result)
    result.seek(0, 0)
    try:
        tarball = TarFile(fileobj=result, mode='r')
        if self.path.exists():
            self.path.remove()
        self.path.createDirectory()
        tarball.extractall(self.path.path)
    except:
        pass
