autopkgtest, DependsPolicy: Run tests where we didn't care about the depends problem

We currently skip running autopkgtests where there is an installability
problem, but in a few cases the depends policy notes these only, but
otherwise doesn't block migration on them.

In these cases, let's try to run the autopkgtests anyway. There will be
a few instances of uninstallability here, but since we migrate the
packages we should give them a chance to be tested.

britney2/policies/autopkgtest.py

@@ -396,7 +396,8 @@ class AutopkgtestPolicy(BasePolicy):
                     verdict = PolicyVerdict.REJECTED_TEMPORARILY
                     self.logger.info('%s hasn''t been built on arch %s, delay autopkgtest there', source_name, arch)
                     excuse.add_verdict_info(verdict, "arch:%s not built yet, autopkgtest delayed there" % arch)
-                elif arch in excuse.unsatisfiable_on_archs:
+                elif (arch in excuse.unsatisfiable_on_archs and
+                      arch not in excuse.policy_info['depends'].get('skip_dep_check', [])):
                     self.logger.info('%s is uninstallable on arch %s, not running autopkgtest there', source_name, arch)
                     excuse.addinfo("uninstallable on arch %s, not running autopkgtest there" % arch)
                 else:

britney2/policies/policy.py

@@ -883,6 +883,8 @@ class DependsPolicy(BasePolicy):
                     # so the autopkgtest policy knows not to try to run tests
                     excuse.add_verdict_info(verdict, "%s/%s has unsatisfiable dependency, but %s so never mind." % (
                         pkg_name, arch, skip_dep_check_reason))
+                    # let the autopkgtest policy see that we did this
+                    deps_info.setdefault('skip_dep_check', []).append(arch)
                     continue
                 verdict = PolicyVerdict.REJECTED_PERMANENTLY
                 excuse.add_verdict_info(verdict, "%s/%s has unsatisfiable dependency" % (