Refactor test_mix_and_match_attack.py.

Refactored to use the 'unittest' module (test conditions in code, rather
than verifying text output), use pre-generated repository files, and
discontinue use of the old repository tools.  Modify the previous scenario
simulated for the mix-and-match attack.
Merge pull request #201 from vladimir-v-diaz/develop

Refactor test_mix_and_match_attack.py