rally.js initialization does not log error clearly enough in non-dev mode

[rhelmer]

I'm getting a very unhelpful generic "Rally initialization failed" message trying to test the Princeton study, digging in with the debugger, really it's because of this:

Uncaught (in promise) Error: Core._handleExternalMessage - No schema namespace specified in remote settings for [email protected]
    initialize moz-extension://62582dc4-5606-5e4e-997f-cc4545e5be0a/dist/background.js:1316
    runStudy moz-extension://62582dc4-5606-5e4e-997f-cc4545e5be0a/dist/background.js:60447
    <anonymous> debugger eval code:1

We should make sure that initialization problems are clearly logged even in non-debug mode.