This issue has already been mentioned here, but it is a quite old question and I couldn't find any other information.
The Request Interceptor of a Retrofit API call is executed on the main thread. This is an issue when dealing with AccountManager to add auth tokens to the request header, like
String token = mAccountManager.blockingGetAuthToken(account, AuthConsts.AUTH_TYPE, false);
Same issue is discussed on G+ and there is a related issue on GitHub here.
While this all gets worked (thanks SquareUp!), what is the best way to work around it? Wrapping the Retrofit calls in an AsyncTask or similar feels like invalidating the whole idea.