Fix cpplint.py to work under Python 3 (#6201)

Author: dconeybe

scripts/check_lint.py

@@ -23,6 +23,7 @@
 import logging
 import os
 import subprocess
+import sys
 import textwrap
 
 from lib import checker
@@ -124,7 +125,7 @@ def _run_cpplint(options, files):
   scripts_dir = os.path.dirname(os.path.abspath(__file__))
   cpplint = os.path.join(scripts_dir, 'cpplint.py')
 
-  command = ['python2', cpplint, '--quiet']
+  command = [sys.executable, cpplint, '--quiet']
   command.extend(options)
   command.extend(files)