Bug 1397847: Pass the taskcluster root to `load_tasks_for_kind` in `mach artifact toolchain`; r=dustin a=tomprince

Differential Revision: https://phabricator.services.mozilla.com/D13433

--HG--
extra : rebase_source : ab46822cbf7cb72de61285eb336cb80356943752
extra : amend_source : 9ec807b18a8cc7d1b5d33cb4a4c65988fee4ff00

python/mozbuild/mozbuild/mach_commands.py

@@ -1313,8 +1313,6 @@ class PackageFrontend(MachCommandBase):
         import requests
         import shutil
 
-        from taskgraph.config import load_graph_config
-        from taskgraph.generator import Kind
         from taskgraph.util.taskcluster import (
             get_artifact_url,
         )
@@ -1433,7 +1431,8 @@ class PackageFrontend(MachCommandBase):
                 strict=False,
             )
 
-            toolchains = load_tasks_for_kind(params, 'toolchain')
+            root_dir = mozpath.join(self.topsrcdir, 'taskcluster/ci')
+            toolchains = load_tasks_for_kind(params, 'toolchain', root_dir=root_dir)
 
             aliases = {}
             for t in toolchains.values():

taskcluster/taskgraph/generator.py

@@ -382,13 +382,13 @@ class TaskGraphGenerator(object):
          )
 
 
-def load_tasks_for_kind(parameters, kind):
+def load_tasks_for_kind(parameters, kind, root_dir=None):
     """
     Get all the tasks of a given kind.
 
     This function is designed to be called from outside of taskgraph.
     """
-    tgg = TaskGraphGenerator(root_dir=None, parameters=parameters, target_kind=kind)
+    tgg = TaskGraphGenerator(root_dir=root_dir, parameters=parameters, target_kind=kind)
     return {
         task.task['metadata']['name']: task
         for task in tgg.full_task_set