Improve error messages regarding track syntax errors

[gareth-ellis]

I've encountered a few cryptic error messages whilst tweeking a track.

Issues this solves:

• If we fail to transform the templates completely due to a syntax error, we write that the full output is listed XXXX - it isnt, we never get round to writing it, so I am catching the TemplateSyntaxError and writing another error message. It would be nice if we can say what the error is, or at least where, but we can't yet. If I find a way I will add that to the PR / a new PR
• If you don't include "operation", you get an Attribute error, but no information where in the track. Now we include a more helpful message that should help users see where the issue may be.

[dpifke-elastic]

LGTM.