Jenkins currently has no indication on whether appstream data is in a shitty state.

There should be a job that eats the data here and convers it into junit output to complain about in a job:
http://metadata.neon.kde.org/appstream/user/hints/xenial/main/

Ideally however this would first see T2971 resolved and appstream enabled for dev/unstable and then validate that. Errors in user are somewhat less interesting as they can't be done much about anyway.