Add invalidated-by-other-package field in excuses.yaml

The other fields related to invalidation are currently not deterministic and
depend on the order in which the excuses are invalidated.

The new invalidated-by-other-package field is just a boolean which shows the
excuse was invalidated by some other package for some reason (without
specifying the reason). It does not depend on the order of processing and
should be deterministic.

Signed-off-by: Ivo De Decker <ivodd@debian.org>

britney2/excuse.py

@@ -304,6 +304,8 @@ class Excuse(object):
                 'on-architectures': sorted(self.missing_builds),
                 'on-unimportant-architectures': sorted(self.missing_builds_ood_arch),
             }
+        if self.invalid_deps or self.invalid_build_deps:
+            excusedata['invalidated-by-other-package'] = True
         if self.deps or self.invalid_deps or self.arch_build_deps or self.indep_build_deps \
                 or self.invalid_build_deps or self.break_deps or self.unsat_deps:
             excusedata['dependencies'] = dep_data = {}