Trailing '==' in a token breaks verify_token()

Hello, As far as I could test it, it seems that using `HTTPTokenAuth` with a custom scheme doesn't support having the string '==' at the end of a token I know it's not an usual token format, so here some exemples: `N2RmYmWmNDY1Nw==` is not recognized in the `verify_token(token)` though `N2RmYmWmNDY1Nw=` OK `N2RmYm==WmNDY1Nw` OK I'm not sure it's a bug, or if it works as intended and the token of a legacy app I use shouldn't be formed like that But I wanted to raise the issue, just in case that's a not wanted behaviour And to give more details, these kind of tokens `N2RmYmWmNDY1Nw==` were perfectly recognized in previous versions (up to ~4.3.0 I'd say) It's reproductible using your documentation and my exemple 'faulty' token: https://flask-httpauth.readthedocs.io/en/latest/#token-authentication-example Inside this block, the variable `token` is `None` ```python @auth.verify_token def verify_token(token): if token in tokens: return tokens[token] ``` Thanks in advance