Set proper result (purple/red) for "Uncaught Exception" and "Failure reason" steps

recipes.py

Index: recipes.py
diff --git a/recipes.py b/recipes.py
index 76538112434b5984c09571a7226edac1c1428773..9b070afb04e738d221cafc93b4a1d5815b521539 100755
--- a/recipes.py
+++ b/recipes.py
@@ -67,12 +67,14 @@ def handle_recipe_return(recipe_result, result_filename, stream_engine):
 
   if 'traceback' in recipe_result.result:
     with stream_engine.new_step_stream('Uncaught Exception') as s:
+      s.set_step_status('EXCEPTION')
       with s.new_log_stream('exception') as l:
         for line in recipe_result.result['traceback']:
           l.write_line(line)
 
   if 'reason' in recipe_result.result:
     with stream_engine.new_step_stream('Failure reason') as s:
+      s.set_step_status('FAILURE')
       with s.new_log_stream('reason') as l:
         for line in recipe_result.result['reason'].splitlines():
           l.write_line(line)