Fix confusing error when something is wrong with the model

Tammo Jan Dijkemarequested to merge
improve-model-parse-error2 into master

Created by: aroffringa

When a model (patch/source name?) contains incorrect symbols, like "(" or "'", DP3 would give the following impossible to understand exception: std exception detected: Regex: invalid regular expression component ( given (Unmatched \()

I've now made sure that the exception is at least mentioning the problem is in the model.

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