Flush failure needs to be reported in UX

[b1conrad]

This is to follow up on issue #568 when flushing a ruleset in the UI, and the ruleset compiles (and so can be registered with the pico-engine) but cannot be installed in a pico.

This can happen if part of the change to the ruleset is use module of another ruleset which is not installed in the pico (whose UI and Rulesets tab is being used to do the flushing).