Improve test failure message when getting more errors than expected

[jfmengels]

    RULE REPORTED MORE ERRORS THAN EXPECTED

    I found 1 error too many for module `A`:

      - `Don't use dedicated translation function`
        at { start = { row = 7, column = 38 }, end = { row = 7, column = 50 } }

It would be helpful if in addition to at, it would say under:

    RULE REPORTED MORE ERRORS THAN EXPECTED

    I found 1 error too many for module `A`:

      - `Don't use dedicated translation function`
        under `someFunction`
        at { start = { row = 7, column = 38 }, end = { row = 7, column = 50 } }

I don't know if we should add more information, such as "details", or not.

[lue-bird]

Adding details would be really helpful!