Since some recent change in 2.8 the UI for rigify is no longer working.
Note: if your object has ANY custom property, the custom property shows as
a Misc. category, it is not particular to rigify, so I will not bother with
this here.
The UI is still using the toolshelf. So I did not bump the version to 2.80.
It seems to be working as far as the UI and the quat/euler operators is concerned.