Add a dry-run option for the autopkgtest policy specifically

For rolling out britney on a new machine, we want to generate update_excuses
and update_output to confirm it's working correctly all the way through, so
we don't want to use the global --dry-run option; but we *do* want to
disable queuing tests and instead let the production instance of britney
queue the tests while we simply query the results.  Add support for
ADT_ENABLE=dry-run in britney.conf, parallelling the behavior of other
policies.

britney.py

@@ -521,8 +521,9 @@ class Britney(object):
         self._policy_engine.add_policy(RCBugPolicy(self.options, self.suite_info))
         if getattr(self.options, 'piuparts_enable', 'yes') == 'yes':
             self._policy_engine.add_policy(PiupartsPolicy(self.options, self.suite_info))
-        if getattr(self.options, 'adt_enable') == 'yes':
+        add_autopkgtest_policy = getattr(self.options, 'adt_enable', 'no')
-            self._policy_engine.add_policy(AutopkgtestPolicy(self.options, self.suite_info))
+        if add_autopkgtest_policy in ('yes', 'dry-run'):
+            self._policy_engine.add_policy(AutopkgtestPolicy(self.options, self.suite_info, dry_run=add_autopkgtest_policy))
         self._policy_engine.add_policy(AgePolicy(self.options, self.suite_info, MINDAYS))
         # XXX this policy results in asymmetric enforcement of
         # build-dependencies in the release pocket (nothing blocks

britney2/policies/autopkgtest.py

@@ -117,7 +117,8 @@ class AutopkgtestPolicy(BasePolicy):
     reject the upload if any of those regress.
     """
 
-    def __init__(self, options, suite_info):
+    def __init__(self, options, suite_info, dry_run=False):
+
         super().__init__('autopkgtest', options, suite_info, {SuiteClass.PRIMARY_SOURCE_SUITE})
         # tests requested in this and previous runs
         # trigger -> src -> [arch]
@@ -126,6 +127,7 @@ class AutopkgtestPolicy(BasePolicy):
         self.testsuite_triggers = {}
         self.result_in_baseline_cache = collections.defaultdict(dict)
         self.database_path = os.path.join(self.state_dir, 'autopkgtest.db')
+        self.dry_run = dry_run
 
         # results map: trigger -> src -> arch -> [passed, version, run_id, seen]
         # - trigger is "source/version" of an unstable package that triggered
@@ -292,7 +294,7 @@ class AutopkgtestPolicy(BasePolicy):
         # Initialize AMQP connection
         self.amqp_channel = None
         self.amqp_file = None
-        if self.options.dry_run:
+        if self.options.dry_run or self.dry_run:
             return
 
         amqp_url = self.options.adt_amqp
@@ -1117,7 +1119,7 @@ class AutopkgtestPolicy(BasePolicy):
         If huge is true, then the request will be put into the -huge instead of
         normal queue.
         '''
-        if self.options.dry_run:
+        if self.options.dry_run or self.dry_run:
             return
 
         params = {'triggers': triggers}