Formally define step config, pass to stream.

recipes.py

 #!/usr/bin/env python
 # Copyright 2015 The LUCI Authors. All rights reserved.
 # Use of this source code is governed under the Apache License, Version 2.0
 # that can be found in the LICENSE file.
 
 """Tool to interact with recipe repositories.
 
 This tool operates on the nearest ancestor directory containing an
 infra/config/recipes.cfg.
 """
@@ skipping 46 matching lines @@
   lint_test.main(universe_view, args.whitelist or [])
 
 
 def handle_recipe_return(recipe_result, result_filename, stream_engine):
   if 'recipe_result' in recipe_result.result:
     result_string = json.dumps(
         recipe_result.result['recipe_result'], indent=2)
     if result_filename:
       with open(result_filename, 'w') as f:
         f.write(result_string)
-    with stream_engine.new_step_stream('recipe result') as s:
+    with stream_engine.make_step_stream('recipe result') as s:
       with s.new_log_stream('result') as l:
         l.write_split(result_string)
 
   if 'traceback' in recipe_result.result:
-    with stream_engine.new_step_stream('Uncaught Exception') as s:
+    with stream_engine.make_step_stream('Uncaught Exception') as s:
       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:
+    with stream_engine.make_step_stream('Failure reason') as s:
       with s.new_log_stream('reason') as l:
         for line in recipe_result.result['reason'].splitlines():
           l.write_line(line)
 
   if 'status_code' in recipe_result.result:
     return recipe_result.result['status_code']
   else:
     return 0
 
 
@@ skipping 478 matching lines @@
   ret = main()
   if not isinstance(ret, int):
     if ret is None:
       ret = 0
     else:
       print >> sys.stderr, ret
       ret = 1
   sys.stdout.flush()
   sys.stderr.flush()
   os._exit(ret)