Exports the database on the server.

    Usage::

        fab prod run_export_db
        fab prod run_export_db:filename=foobar.dump

def run_export_db(filename=None):
    """
    Exports the database on the server.

    Usage::

        fab prod run_export_db
        fab prod run_export_db:filename=foobar.dump

    """
    if not filename:
        filename = settings.DB_DUMP_FILENAME
    with cd(settings.FAB_SETTING('SERVER_PROJECT_ROOT')):
        run_workon('fab export_db:remote=True,filename={}'.format(filename))