Switch to yaml.safe_load

We only deal with simple types.

Change-Id: Ic902b19dc8db9d0e1e3dab0909dfd2400a169c49
diff --git a/tests/make_playbooks.py b/tests/make_playbooks.py
index 12d9e71..33d45ca 100755
--- a/tests/make_playbooks.py
+++ b/tests/make_playbooks.py
@@ -39,7 +39,7 @@
         if os.path.exists(os.path.join(path, fn)):
             config_path = os.path.join(path, fn)
             break
-    config = yaml.load(open(config_path))
+    config = yaml.safe_load(open(config_path))
     for block in config:
         if 'job' not in block:
             continue