The error resulting from match_nodes! is not very insightful

[mlaveaux]

When none of the arms of a match_nodes match the following error is printed Nodes didn't match any pattern: [RegFrm]. However, this error does not come with a stack trace, making it very hard to figure out where the error actually occurs. Either pest_consume can be extended to use MCRL3Error, or the parsing itself can be amended to add a stack trace.