removed a rescue TooComplexToTranslateError

It was not needed anyway since we started using scope.clear.

It would require a @source_rewriter.transaction block
to be correct, BUT transactions cannot be nested :-( as a RuntimeError
told me.

For the case where we do use TooComplexToTranslateError,
we hope people will not nest rescue clauses.
Fixed understanding :defs (cannot call on_def super)
Merge remote-tracking branch 'origin/master'