Make blink_trybot recipe work on windows

scripts/slave/recipe_modules/rietveld/api.py

Index: scripts/slave/recipe_modules/rietveld/api.py
diff --git a/scripts/slave/recipe_modules/rietveld/api.py b/scripts/slave/recipe_modules/rietveld/api.py
index 1cf4e7e9ac969d9f05feae637837f090c2d0398c..82936dc9ff5e10bf00522bd8120d1f11784eca27 100644
--- a/scripts/slave/recipe_modules/rietveld/api.py
+++ b/scripts/slave/recipe_modules/rietveld/api.py
@@ -6,11 +6,12 @@ from slave import recipe_api
 
 class RietveldApi(recipe_api.RecipeApi):
   def apply_issue(self, *root_pieces):
-    return self.m.step('apply_issue', [
-        self.m.path.depot_tools('apply_issue'),
+    return self.m.python('apply_issue',
+        self.m.path.depot_tools('apply_issue.py'), [
         '-r', self.m.path.checkout(*root_pieces),
         '-i', self.m.properties['issue'],
         '-p', self.m.properties['patchset'],
         '-s', self.m.properties['rietveld'],
-        '-e', 'commit-bot@chromium.org'])
+        '-e', 'commit-bot@chromium.org',
+        '--no-commit'])