Switch outcome analysis to enforcing that all tests are executed

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
diff --git a/tests/scripts/analyze_outcomes.py b/tests/scripts/analyze_outcomes.py
index ee14826..58e21e3 100755
--- a/tests/scripts/analyze_outcomes.py
+++ b/tests/scripts/analyze_outcomes.py
@@ -14,9 +14,7 @@
 
 
 class CoverageTask(outcome_analysis.CoverageTask):
-    # We'll populate IGNORED_TESTS soon. In the meantime, lack of coverage
-    # is just a warning.
-    outcome_analysis.FULL_COVERAGE_BY_DEFAULT = False
+    """Justify test cases that are never executed."""
 
     @staticmethod
     def _has_word_re(words: typing.Iterable[str],