Fix up octal use in nvda_chrome_tests.py to run under Python 3.

Bug: 742592
Change-Id: I5d263b00a4d5d1ab0489217f09e73a353c3021b0
Reviewed-on: https://chromium-review.googlesource.com/599568Reviewed-by: Alice Boxhall <aboxhall@chromium.org>
Commit-Queue: Doug Turner <dougt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491780}

tools/accessibility/nvda/nvda_chrome_tests.py

@@ -63,7 +63,7 @@ class NvdaChromeTest(unittest.TestCase):
       os.remove(NVDA_LOGPATH)
     if os.access(CHROME_PROFILES_PATH, os.F_OK):
       shutil.rmtree(CHROME_PROFILES_PATH)
-    os.mkdir(CHROME_PROFILES_PATH, 0777)
+    os.mkdir(CHROME_PROFILES_PATH, 0o777)
 
     def handler(signum, frame):
       print('Test interrupted, attempting to kill subprocesses.')