structured: convert to python3 only
All users of these modules are python3 only already.
BUG=chromium:997354
TEST=`./run_tests` passes
Change-Id: I5a81115292f5614de55f8a85372588a73771003d
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/2658797
Reviewed-by: Sergey Frolov <sfrolov@google.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/lib/structured.py b/lib/structured.py
index 389c02e..a5b2c23 100644
--- a/lib/structured.py
+++ b/lib/structured.py
@@ -7,6 +7,12 @@
from __future__ import print_function
+import sys
+
+
+assert sys.version_info >= (3, 6), 'This module requires Python 3.6+'
+
+
_BUILTINS = (str, int, float, bool, type(None))
