[kea-dev] check exception messages

[Francis Dupont]

The idea to extend gtest with new macros checking exception messages
(#3889) was not adopted but the idea is still applicable by writing
explicit checks as the moduleSpecError() routine in
src/lib/config/tests/module_spec_unittests.cc

So I propose:
 - to add something about this in coding guidelines, e.g.:
  when the same exception can be raised with different and sensible
  error messages these messages should be explicitly checked
  in unit tests.

 - create a new ticket to address cases which clearly should be improved.

Regards

Francis Dupont <fdupont at isc.org>