Fix presubmit following https://crrev.com/c/3611486 Switch to python3 for to get expected dict.keys() ordering python behavior/spec changed around ~3.6-3.7 https://stackoverflow.com/a/40007169 Reorder mixins that got out of order. Bug: angleproject:7242 Change-Id: I5fbc973ccc52b11f7db55c50e2ae7af54361dd40 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3622053 Auto-Submit: Roman Lavrov <romanl@google.com> Commit-Queue: Jamie Madill <jmadill@chromium.org> Commit-Queue: Roman Lavrov <romanl@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>