'Get a file from the control dir with a specific name.
Although the filename should be interpreted as a filename relative to
the control dir in a disk-baked Repo, the object returned need not be
pointing to a file in that location.
:param path: The path to the file, relative to the control dir.
:return: An open file object, or None if the file does not exist.'

def get_named_file(self, path):

    contents = self._named_files.get(path, None)
    if (contents is None):
        return None
    return BytesIO(contents)
