Ennru forward reference error

[ennru]

@felixmulder
Another awsome error message giving more relevant context.

There seem to be other checks for this error around that expect the old message, but I did not find out how to run those tests.

I removed the ctx.debuglog as that symbol is now included in the message.

[felixmulder]

@liufengyun - debug test failing in this build. Could you investigate?

[liufengyun]

@felixmulder I just restarted the test, seems to be some non-determinism. I have reduced the probability it can happen last week. If it happens > 5%, I am happy to disable it for the moment, until I figure out a solution.

[felixmulder]

@liufengyun - I'll be at the office in an hour, let's talk about it then. I'd like to eliminate the non-determinism if possible: in a couple of years this knowledge could be lost.

[felixmulder]

Thanks @ennru !