Something we bumped into when upgrading from corda 2 to 3 is that:
we (Cordapp devs) are all using the structure in the corda Kotlin template
the Kotlin template includes a copy of quasar.jar in the lib dir
we didn't think to upgrade this when we changed our corda version
I think we should include this in the release notes. I know this is a minor thing but it would help us.
Possibly we should turn this jira into: make Kotlin template download quasar. But as you have to specify the `-javagent:lib/quasar.jar` every time you run a test in intelliJ, this requires some thinking!
Hope this is useful. Apols if I've missed the relevant upgrade step.