Bug 1388478 - Load tests.yml tasks with the transform loader, r=dustin

This will allow us to use 'jobs', 'jobs-from' and 'job-defaults' with the test
kind.

MozReview-Commit-ID: 7q66kjSI4b3

--HG--
extra : rebase_source : 46c46b1a02d74a1e953c878de2fbb6cbb1b5dd81

taskcluster/ci/test/kind.yml

@@ -9,3 +9,6 @@ transforms:
    - taskgraph.transforms.job:transforms
    - taskgraph.transforms.coalesce:transforms
    - taskgraph.transforms.task:transforms
+
+jobs-from:
+   - tests.yml

taskcluster/taskgraph/loader/test.py

@@ -7,6 +7,7 @@ from __future__ import absolute_import, print_function, unicode_literals
 import copy
 import logging
 
+from .transform import loader as transform_loader
 from ..util.yaml import load_yaml
 
 logger = logging.getLogger(__name__)
@@ -39,7 +40,8 @@ def loader(kind, path, config, params, loaded_tasks):
     test_platforms = expand_tests(test_sets_cfg, test_platforms)
 
     # load the test descriptions
-    test_descriptions = load_yaml(path, 'tests.yml', enforce_order=True)
+    tests = transform_loader(kind, path, config, params, loaded_tasks)
+    test_descriptions = {t.pop('name'): t for t in tests}
 
     # generate all tests for all test platforms
     for test_platform_name, test_platform in test_platforms.iteritems():

taskcluster/taskgraph/transforms/tests.py

@@ -168,6 +168,9 @@ test_description_schema = Schema({
     # common attributes)
     Optional('attributes'): {basestring: object},
 
+    # relative path (from config.path) to the file task was defined in
+    Optional('job-from'): basestring,
+
     # The `run_on_projects` attribute, defaulting to "all".  This dictates the
     # projects on which this task should be included in the target task set.
     # See the attributes documentation for details.