util.crypto: Ensure signing parameter is a string lua_tostring() returns NULL if the specified value is missing or can't become a string. luaL_checkstring() will raise an error. We prefer the latter behaviour, otherwise we end up passing NULL to OpenSSL.

module:log("error", "mod_pep_plus has been renamed to mod_pep, please update your config file. Auto-loading mod_pep...");
module:depends("pep");