introduce recipe_exception in result.proto

recipes.py

Index: recipes.py
diff --git a/recipes.py b/recipes.py
index 0626c1f356f2ef24611b9eab21b59192bc8d006c..8a0ad7417434c73140328d949465efe5221671cf 100755
--- a/recipes.py
+++ b/recipes.py
@@ -158,7 +158,14 @@ def new_handle_recipe_return(result, result_filename, stream_engine):
   if result.HasField('failure'):
     f = result.failure
     if f.HasField('exception'):
-      with stream_engine.make_step_stream('Uncaught Exception') as s:
+      with stream_engine.make_step_stream(
+          'Uncaught Exception in recipe engine') as s:
+        s.add_step_text(f.human_reason)
+        with s.new_log_stream('exception') as l:
+          for line in f.exception.traceback:
+            l.write_line(line)
+    elif f.HasField('recipe_exception'):
+      with stream_engine.make_step_stream('Uncaught Exception in recipe') as s:
         s.add_step_text(f.human_reason)
         with s.new_log_stream('exception') as l:
           for line in f.exception.traceback: