website_twitter: authentication error popup with proper description base on twitter error code and responses

<b>Purpose:</b> For getting proper error message (If user enter invalid API key or secret, tweet is protected  can not getting tweets, Invalid Authorization, Something is misconfiguration)

<b>Task:</b> https://www.odoo.com/web#id=8677&view_type=form&model=project.task&menu_id=3942&action=327
<b>Pad:</b> https://pad.odoo.com/p/r.O5ZH6hmk5EQokj5t
can you store all the error messages into constants at the top of the file ? it will be more consistent with exception codes