Allowed invalid message to be overridden in ESIdentityCardNumberField.

[benkonrath]

Fixes #336

[codecov-io]

Codecov Report

Merging #339 into master will not change coverage.
The diff coverage is 100%.

@@           Coverage Diff           @@
##           master     #339   +/-   ##
=======================================
  Coverage   95.89%   95.89%           
=======================================
  Files         153      153           
  Lines        3851     3851           
  Branches      512      512           
=======================================
  Hits         3693     3693           
  Misses         96       96           
  Partials       62       62

Impacted Files	Coverage Δ
localflavor/es/forms.py	100% <100%> (ø)	⬆️

---

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 c5ebe91...3ff5ab0. Read the comment docs.