fix_encoding: Do unicode type checks only on Python 2
fix_encoding: Do unicode type checks only on Python 2

The unicode type doesn't exist in Python 3, because everything's Unicode.

This would resulted in the following error on Python 3:
<Unicode console <stderr>>.write: NameError("name 'unicode' is not defined")

Bug: 942522
Change-Id: I3e90d078df64abcec2c79aa69881deea40ff7d01
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1701401
Reviewed-by: Dirk Pranke <6693ee08b084bb2ffa767f664c99b689395e0e4b@chromium.org>
Commit-Queue: Raul Tambre <8b52b6b714585648fd300da0dbc0fa0678553280@tambre.ee>
Auto-Submit: Raul Tambre <8b52b6b714585648fd300da0dbc0fa0678553280@tambre.ee>

CoherentLabs/depot_tools,CoherentLabs/depot_tools