rework python scripts to support Python 2 & 3

We run the unittests in both python versions to maintain coverage,
and we run things through `cros lint` during upload to help prevent
regressions.

We also switch the default to Python 3 to keep people on their toes.

BUG=chromium:982465
TEST=running unittests against python2 & python3 pass
TEST=`./fmap.py bin/example.bin` through python2 & python3 works

Change-Id: I79f0ce59664ea42dfa18e45ccde0dffc0c18227d
Reviewed-on: https://chromium-review.googlesource.com/1693888
Tested-by: Mike Frysinger <[email protected]>
Commit-Ready: Mike Frysinger <[email protected]>
Legacy-Commit-Queue: Commit Bot <[email protected]>
Reviewed-by: Duncan Laurie <[email protected]>
3 files changed