I'm using signpost, an OAuth library for Java, to authenticate with Yahoo in order to use the Contacts API. My code works fine if I don't try to use the xoauth_lang_pref parameter to specify the locale of the login page the user will see. If I do add that parameter I get a 401 back when I try to get the request token. An example of the URL I'm using is:
https://api.login.yahoo.com/oauth/v2/get_re...lang_pref=fr_CAAgain, if I were not to include "&xoauth_lang_pref=fr_CA" the request works.