Backup database and associate it with current release

def backup_db(release=None, limit=5):
    """
    Backup database and associate it with current release
    """

    assert "mysql_user" in env, "Missing mysqL_user in env"
    assert "mysql_password" in env, "Missing mysql_password in env"
    assert "mysql_host" in env, "Missing mysql_host in env"
    assert "mysql_db" in env, "Missing mysql_db in env"

    if not release:
        release = paths.get_current_release_name()

    max_versions = limit+1

    if not release:
        return

    env.run("mkdir -p %s" % paths.get_backup_path("mysql"))

    backup_file = "mysql/%s.sql.gz" % release
    backup_path = paths.get_backup_path(backup_file)

    env.run("mysqldump -u %s -p%s -h %s %s | gzip -c > %s" %
            (env.mysql_user, env.mysql_password, env.mysql_host, env.mysql_db,
             backup_path))

    # Remove older releases
    env.run("ls -dt %s/* | tail -n +%s | xargs rm -rf" % (
        paths.get_backup_path("mysql"),
        max_versions)
    )