[Exercise 10 - Links] Test failure message should be concise and helpful

[R-V-S]

I had a student that was stuck on the 2nd spec because they had omitted the period in the sentence, and this is the error message they received:

A shorter and clearer error message would go a long way towards helping them troubleshoot the issue. I'm also not sure that spelling and grammatical mistakes should fail them. (On the one hand, precision matters in programming; on the other hand, it can feel like a distraction from the lesson at hand).