* add overrides for what()
* translation fot KeyErrorException; update tests
* Switch all exceptions to `const char *` as a return type from message() (#4)
* switch return type of message() from std::string to const char *
* adjust one test to the new return type from message()
remove unnecessary verbosity from some tests
* fix cartridge build: update call to message().c_str()
* rebase agains master; fix another issue in cartridge build
* add deprecation note for message() and getMessage()
* amend Release notes
Co-authored-by: Greg Landrum <greg.landrum@gmail.com>
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