[depot_tools] Fix timestamp issues related to local auth

Bug: 509672
Change-Id: I5abb813d5f78291b4bf2d8e856c6fd71fcad5b68
Reviewed-on: https://chromium-review.googlesource.com/791472
Commit-Queue: Mun Yong Jang <myjang@google.com>
Reviewed-by: Nodir Turakulov <nodir@chromium.org>
diff --git a/auth.py b/auth.py
index 11a2113..c415610 100644
--- a/auth.py
+++ b/auth.py
@@ -200,11 +200,17 @@
   if expiry:
     try:
       expiry_dt = datetime.datetime.utcfromtimestamp(expiry)
+      logging.debug(
+        'local_auth: got an access token for '
+        'account "%s" that expires in %d sec',
+        account_id, (expiry_dt - now).total_seconds())
     except (TypeError, ValueError):
       authErr('Invalid expiry in returned token')
-  logging.debug(
-      'local_auth: got an access token for account "%s" that expires in %d sec',
-      account_id, expiry - time.mktime(now.timetuple()))
+  else:
+    logging.debug(
+        'local auth: got an access token for '
+        'account "%s" that does not expire',
+        account_id)
   access_token = AccessToken(access_token, expiry_dt)
   if _needs_refresh(access_token, now=now):
     authErr('local_auth: the returned access token needs to be refreshed')