gerrit: handle unicode messages
gerrit: handle unicode messages

Using str() on unicode strings fails.  Tweak how we do things to work
with both ascii and utf-8 and integers.

BUG=None
TEST=`USER=marcheu gerrit todo` works (handles message in CL:60715)

Change-Id: I20bd116c31e5383fa95b26f6a33d51c1052ea3af
Reviewed-on: https://chromium-review.googlesource.com/173812
Reviewed-by: Stéphane Marchesin <e16f69845633a0cf74affe1e5a677caa6296c937@chromium.org>
Tested-by: Stéphane Marchesin <e16f69845633a0cf74affe1e5a677caa6296c937@chromium.org>

bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite