test: promote --train to its own subcommand

unittests/repo_test_util.py

 # Copyright 2016 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.
 
 """Utilities for testing with real repos (e.g. git)."""
 
 
 import contextlib
 import os
 import shutil
@@ skipping 189 matching lines @@
     with in_directory(repo['root']):
       args = [
           sys.executable, self._recipe_tool,
           '--package', os.path.join(
               repo['root'], 'infra', 'config', 'recipes.cfg'),
       ]
       for repo, path in overrides:
         args.extend(['-O', '%s=%s' % (repo, path)])
       args.extend([
           '--use-bootstrap',
-          'test', 'run', '--train',
+          'test', 'train',
       ])
       subprocess.check_output(args, stderr=subprocess.STDOUT)
 
   def update_recipe(self, repo, name, deps, calls):
     """Updates or creates a recipe in given repo.
     Commits the change.
 
     Arguments:
       repo(dict): one of the repos returned by |repo_setup|
       name(str): name of the recipe (without .py)
@@ skipping 94 matching lines @@
       message = ' '.join(
         ['update %r recipe_module: ' % name] +
         ['%s(%s)' % t for t in methods.iteritems()]
       )
       return self.commit_in_repo(repo, message)
 
   def reset_repo(self, repo, revision):
     """Resets repo contents to given revision."""
     with in_directory(repo['root']):
       subprocess.check_output(['git', 'reset', '--hard', revision])