rna-transcription : add specific text error on expect_error

[amoradell]

Testing a to_rna solution with tio.run, I got a syntax error before stop() because student tests empty string instead of null.

Would it be possible to add a second argument to expect_error(to_rna(dna)) ?

Like expect_error(to_rna(dna), "invalid input")

[katrinleinweber]

Hello and thanks for this report :-)

Please read through the guide to contributing to test suites. I'm open to reviewing a PR that adds such a test to just the R track, if it isn't relevant to the problem spec generally.