Fail gracefully when dm.json is not present

platform_tools/android/tradefed/upload_dm_results.py

Index: platform_tools/android/tradefed/upload_dm_results.py
diff --git a/platform_tools/android/tradefed/upload_dm_results.py b/platform_tools/android/tradefed/upload_dm_results.py
index 9aac4075808240f6a1af91588e824e413fb16242..a8ca01e64c601463c6421b36f1cec504f469840d 100755
--- a/platform_tools/android/tradefed/upload_dm_results.py
+++ b/platform_tools/android/tradefed/upload_dm_results.py
@@ -32,6 +32,9 @@ def main(dm_dir, build_number, builder_name):
     gs_utils.GSUtils.Permission.READ
   )]
 
+  if not os.path.isfile(os.path.join(dm_dir, 'dm.json')):
+    sys.exit("no dm.json file found in output directory.")
+
   # Move dm.json to its own directory to make uploading it easier.
   tmp = tempfile.mkdtemp()
   shutil.move(os.path.join(dm_dir, 'dm.json'),