[code-health] Migrate presubmit to python3

Bug: 1313804
Change-Id: Ie30a7122af23d28ad667871cf61bccf27c005146
diff --git a/PRESUBMIT.py b/PRESUBMIT.py
index bcf853c..13fd383 100644
--- a/PRESUBMIT.py
+++ b/PRESUBMIT.py
@@ -3,6 +3,8 @@
 # found in the LICENSE file.
 """Presubmit script for nasm repository."""
 
+USE_PYTHON3 = True
+
 
 def _WarnIfGitIgnoreHasSources(input_api, output_api):
   """Warn if .gitignore has source files in it."""