Remove recipe warnings due to python module.

The python module is deprecated in favor of using the step module with
an explicit python binary. Switching the code to use the step module and
remove DEPS on recipe_engine/python removes warnings when running recipe
tests in the repo.

Change-Id: If3c9d5d6aff5aab69898b535399accbef92f5c0b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/3880624
Commit-Queue: Garrett Beaty <gbeaty@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

recipes/recipe_modules/git_cl/__init__.py

@@ -1,7 +1,7 @@
 PYTHON_VERSION_COMPATIBILITY = 'PY2+3'
 
 DEPS = [
-  'recipe_engine/context',
-  'recipe_engine/python',
-  'recipe_engine/raw_io',
+    'recipe_engine/context',
+    'recipe_engine/raw_io',
+    'recipe_engine/step',
 ]

recipes/recipe_modules/git_cl/api.py

@@ -16,10 +16,9 @@ class GitClApi(recipe_api.RecipeApi):
       name = name + ' (%s)' % kwargs.pop('suffix')
 
     my_loc = self.c.repo_location if self.c else None
+    cmd = ['vpython', self.repo_resource('git_cl.py'), subcmd] + args
     with self.m.context(cwd=self.m.context.cwd or my_loc):
-      return self.m.python(
-          name, self.repo_resource('git_cl.py'), [subcmd] + args,
-          venv=True, **kwargs)
+      return self.m.step(name, cmd, **kwargs)
 
   def get_description(self, patch_url=None, **kwargs):
     """DEPRECATED. Consider using gerrit.get_change_description instead."""