[autotest] Fix issue with logging error formatting

TEST=Local moblab testing
BUG=chromium:869438

Change-Id: Ie9b866699c61fcf88e28b9d3ee90fdefc47b48d4
Reviewed-on: https://chromium-review.googlesource.com/1158849
Commit-Ready: Keith Haddow <haddowk@chromium.org>
Tested-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Allen Li <ayatane@chromium.org>
(cherry picked from commit f9ae33ff5bbcdeb7d38fc0c4fca005ae2ff1d63c)
Reviewed-on: https://chromium-review.googlesource.com/1162463
Reviewed-by: Keith Haddow <haddowk@chromium.org>
Commit-Queue: Keith Haddow <haddowk@chromium.org>
Trybot-Ready: Keith Haddow <haddowk@chromium.org>
diff --git a/tko/job_serializer.py b/tko/job_serializer.py
index 08b7f66..b7fa0f1 100755
--- a/tko/job_serializer.py
+++ b/tko/job_serializer.py
@@ -441,6 +441,6 @@
                 value = vartype()
             elif not isinstance(value, vartype):
                 logging.warning('Unexpected type %s for attr %s, should be %s',
-                                (type(value), attr, vartype))
+                                type(value), attr, vartype)
 
             setattr(var, attr, vartype(value))