fix unit tests in a clean environment

        data_home_db = os.path.join(xdg_base_dirs.xdg_data_home, 'feed2exec.db')

        if os.path.exists(data_home_db):

            return data_home_db

        else:

        elif os.path.exists(cache_home_db):

            # we use warnings here because this function is likely to

            # be called before the logging module is initialized,

            # which typicall creates a StreamHandler that's not

                DeprecationWarning,

            )

            return cache_home_db

        else:

            # if no DB exists, fallback on the good one

            return data_home_db

    def get(self, key):

        with self.connection(commit=False) as con: