Revert of [recipe_modules/step] do not set cwd if it is start_dir.

recipe_modules/step/example.py

 # Copyright 2013 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.
 
 from recipe_engine import recipe_api, config
 
 DEPS = [
   'path',
   'properties',
   'step',
 ]
 
 
 RETURN_SCHEMA = config.ReturnSchema(
   test_me=config.Single(int)
 )
 
 
 PROPERTIES = {
   'bad_return': recipe_api.Property(default=False),
+  'raise_infra_failure': recipe_api.Property(default=False),
   'access_invalid_data': recipe_api.Property(default=False),
   'timeout': recipe_api.Property(default=0, kind=int),
 }
 
 
-def RunSteps(api, bad_return, access_invalid_data, timeout):
+def RunSteps(
+    api, bad_return, raise_infra_failure, access_invalid_data, timeout):
   if bad_return:
     return RETURN_SCHEMA.new(test_me='this should fail')
   elif timeout:
     # Timeout causes the recipe engine to raise an exception if your step takes
     # longer to run than you allow. Units are seconds.
     if timeout == 1:
       api.step('timeout', ['sleep', '20'], timeout=1)
     elif timeout == 2:
       try:
         api.step('caught timeout', ['sleep', '20'], timeout=1)
       except api.step.StepTimeout:
         return RETURN_SCHEMA(test_me=4)
 
 
   # TODO(martinis) change this
   # The api.step object is directly callable.
   api.step('hello', ['echo', 'Hello World'])
   api.step('hello', ['echo', 'Why hello, there.'])
 
-  # You can change the current working directory as well
-  api.step('mk subdir', ['mkdir', 'something'])
-  with api.step.context({'cwd': api.path['start_dir'].join('something')}):
-    api.step('something', ['bash', '-c', 'echo Why hello, there, in a subdir.'])
-
-  # By default, all steps run in 'start_dir', or the cwd of the recipe engine
-  # when the recipe begins. Because of this, setting cwd to start_dir doesn't
-  # show anything in particular in the expectations.
-  with api.step.context({'cwd': api.path['start_dir']}):
-    api.step('start_dir ignored', ['bash', '-c', 'echo what happen'])
-
   # You can also manipulate various aspects of the step, such as env.
   # These are passed straight through to subprocess.Popen.
   # Also, abusing bash -c in this way is a TERRIBLE IDEA DON'T DO IT.
   with api.step.context({'env': {'friend': 'Darth Vader'}}):
     api.step('goodbye', ['bash', '-c', 'echo Good bye, $friend.'])
 
   # You can modify environment in terms of old environment. Environment
   # variables are substituted in for expressions of the form %(VARNAME)s.
   with api.step.context({'env': {'PATH': api.path.pathsep.join(
       [str(api.step.package_repo_resource()), '%(PATH)s'])}}):
@@ skipping 10 matching lines @@
   step_result.presentation.logs['the reason'] = ['The reason\nit failed']
 
   # Without a command, a step can be used to present some data from the recipe.
   step_result = api.step('Just print stuff', cmd=None)
   step_result.presentation.logs['more'] = ['More stuff']
 
   try:
     api.step('goodbye', ['echo', 'goodbye'])
     # Modifying step_result now would raise an AssertionError.
   except api.step.StepFailure:
-    # Raising anything besides StepFailure or StepWarning causes the build to go
+    # Raising anything besides StepFailure or StepWarning causes the build to go 
     # purple.
     raise ValueError('goodbye must exit 0!')
 
   try:
     api.step('warning', ['echo', 'warning'])
   except api.step.StepFailure as e:
     e.result.presentation.status = api.step.WARNING
     raise api.step.StepWarning(e.message)
 
 
@@ skipping 61 matching lines @@
     )
 
   yield (
       api.test('invalid_access') +
       api.properties(access_invalid_data=True) +
       api.expect_exception('StepDataAttributeError')
     )
 
   yield (
       api.test('infra_failure') +
+      api.properties(raise_infra_failure=True) +
       api.step_data('cleanup', retcode=1)
     )
 
   yield (
       api.test('bad_return') +
       api.properties(bad_return=True) +
       api.expect_exception('TypeError')
     )
 
   yield (
       api.test('timeout') +
       api.properties(timeout=1) +
       api.step_data('timeout', times_out_after=20)
     )
 
   yield (
       api.test('catch_timeout') +
       api.properties(timeout=2) +
       api.step_data('caught timeout', times_out_after=20)
     )