Bug 1469687 - Handle EXIT_PURGE_CACHES in all run-task tasks; r=tomprince

Any run-task task could exit with EXIT_PURGE_CACHES and expect the
task to be retried. Before this commit, we only registered this exit
code for tasks "using: run-task." That excluded mozharness and
a handful of other "using" flavors.

With this commit, we register the exit codes for all run-task tasks
by sniffing for the presence of run-task in the low-level code that
emits the task definition. This should prevent run-tasks tasks
from falling through the cracks and not having their exit codes
result in meaningful behavior.

Differential Revision: https://phabricator.services.mozilla.com/D1715

taskcluster/taskgraph/transforms/task.py

@@ -786,6 +786,17 @@ def build_docker_worker_payload(config, task, task_def):
     if 'max-run-time' in worker:
         payload['maxRunTime'] = worker['max-run-time']
 
+    run_task = payload.get('command', [''])[0].endswith('run-task')
+
+    # run-task exits EXIT_PURGE_CACHES if there is a problem with caches.
+    # Automatically retry the tasks and purge caches if we see this exit
+    # code.
+    # TODO move this closer to code adding run-task once bug 1469697 is
+    # addressed.
+    if run_task:
+        worker.setdefault('retry-exit-status', []).append(72)
+        worker.setdefault('purge-caches-exit-status', []).append(72)
+
     payload['onExitStatus'] = {}
     if 'retry-exit-status' in worker:
         payload['onExitStatus']['retry'] = worker['retry-exit-status']
@@ -802,8 +813,6 @@ def build_docker_worker_payload(config, task, task_def):
             }
         payload['artifacts'] = artifacts
 
-    run_task = payload.get('command', [''])[0].endswith('run-task')
-
     if isinstance(worker.get('docker-image'), basestring):
         out_of_tree_image = worker['docker-image']
         run_task = run_task or out_of_tree_image.startswith(