Add a script to run .taskcluster.yml expansion offline

That file’s logic is getting kinda complex

etc/taskcluster/simulate_github_events.py

@@ -0,0 +1,72 @@
+#!/bin/bash
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at https://mozilla.org/MPL/2.0/.
+
+''''set -e
+cd "$(dirname $0)"
+exec ../../python/_virtualenv/bin/python "$(basename $0)"
+'''
+
+try:
+    import jsone
+except ImportError:
+    import sys
+    sys.exit("pip install git+https://github.com/taskcluster/json-e")
+
+import yaml
+import json
+
+template = yaml.load(open("../../.taskcluster.yml").read().decode("utf8"))
+repo = dict(
+    repository=dict(
+        clone_url="https://github.com/servo/servo.git",
+    ),
+)
+contexts = [
+    dict(
+        tasks_for="github-release",
+        event=repo,
+    ),
+    dict(
+        tasks_for="github-pull-request",
+        event=dict(
+            action="comment",
+            **repo
+        ),
+    ),
+    dict(
+        tasks_for="github-push",
+        event=dict(
+            ref="refs/heads/master",
+            compare="https://github.com/servo/servo/compare/1753cda...de09c8f",
+            after="de09c8fb6ef87dec5932d5fab4adcb421d291a54",
+            pusher=dict(
+                name="bors-servo",
+            ),
+            **repo
+        ),
+    ),
+    dict(
+        tasks_for="github-pull-request",
+        event=dict(
+            action="synchronize",
+            pull_request=dict(
+                number=22583,
+                url="https://github.com/servo/servo/pull/22583",
+                head=dict(
+                    sha="51a422c9ef47420eb69c802643b7686bdb498652",
+                ),
+                merge_commit_sha="876fcf7a5fe971a9ac0a4ce117906c552c08c095",
+            ),
+            sender=dict(
+                login="jdm",
+            ),
+            **repo
+        ),
+    ),
+]
+for context in contexts:
+    print(context["tasks_for"])
+    print(json.dumps(jsone.render(template, context), indent=2))