Test and document how to override specific error messages with translations.

[jwag956]

closes: #450

[codecov]

Codecov Report

Merging #472 (b5f5f86) into master (0c653d5) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #472   +/-   ##
=======================================
  Coverage   97.91%   97.91%           
=======================================
  Files          24       24           
  Lines        3171     3171           
=======================================
  Hits         3105     3105           
  Misses         66       66           

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0c653d5...b5f5f86. Read the comment docs.