Exports the media folder on the server.

    Usage::

        fab prod run_export_media
        fab prod run_export_media:filename=foobar.tar.gz

def run_export_media(filename=None):
    """
    Exports the media folder on the server.

    Usage::

        fab prod run_export_media
        fab prod run_export_media:filename=foobar.tar.gz

    """
    if not filename:
        filename = settings.MEDIA_DUMP_FILENAME

    with cd(settings.FAB_SETTING('SERVER_MEDIA_ROOT')):
        run('rm -rf {0}'.format(filename))
        run('tar -czf {0} *'.format(filename))
        run('mv {0} {1}'.format(
            filename, settings.FAB_SETTING('SERVER_MEDIA_BACKUP_DIR')))