of database (see :meth:`get_path`), or else should be an absolute
path with initial components that match the path of 'database'.
:returns: :class:`Directory` or raises an exception.
- :raises:
- :exc:`NotmuchError` with :attr:`STATUS`.FILE_ERROR
- If path is not relative database or absolute with initial
- components same as database.
+ :raises: :exc:`FileError` if path is not relative database or absolute
+ with initial components same as database.
"""
self._assert_db_is_initialized()
# sanity checking if path is valid, and make path absolute