Tidy some assertions in caps_helper.py
Tidy some assertions in caps_helper.py

These triggered while I was experimenting with different places to put
the test name, and I thought I'd fix them up.

mlundblad/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,jku/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,Ziemin/telepathy-gabble,mlundblad/telepathy-gabble,jku/telepathy-gabble,jku/telepathy-gabble