presubmit: add depot_tools to PATH

recipe_modules/presubmit/api.py

Index: recipe_modules/presubmit/api.py
diff --git a/recipe_modules/presubmit/api.py b/recipe_modules/presubmit/api.py
index 3fbf3169091346aeb45df1064ff2a6327c099fca..99fe4d72784adc5253ffd741261d0d42fedf9ba1 100644
--- a/recipe_modules/presubmit/api.py
+++ b/recipe_modules/presubmit/api.py
@@ -7,7 +7,14 @@ from recipe_engine import recipe_api
 class PresubmitApi(recipe_api.RecipeApi):
   def __call__(self, *args, **kwargs):
     """Return a presubmit step."""
+
     name = kwargs.pop('name', 'presubmit')
+
+    kwargs.setdefault('env', {})
+    kwargs['env'].setdefault('PATH', '%(PATH)s')
+    kwargs['env']['PATH'] = self.m.path.pathsep.join([
+        kwargs['env']['PATH'], str(self._module.PACKAGE_DIRECTORY)])
+
     return self.m.python(
         name, self.package_resource('presubmit_support.py'), list(args),
         **kwargs)