Reland "git-cl: Fix some python3 compatibility errors."

This is a reland of c87ed606
Fix on the reland: Encode change description before writing to temporary file.

Original change's description:
> git-cl: Fix some python3 compatibility errors.
>
> Also, fix bug in git cl status where the 'updated' field was used to compare messages, even though
> it doesn't exist (see [1]). This CL modifies it to use 'date', which does exist.
>
> [1] https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#change-message-info
>
> Bug: 1002209
> Change-Id: I5a5e1193b8502c3ad35d94808ea178cad7f44ac6
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1891259
> Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
> Reviewed-by: Anthony Polito <apolito@google.com>

Bug: 1002209
Change-Id: I2f0fc779ea3e361e6d32ee7ce1e53cbddb5cfdea
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1898702
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Anthony Polito <apolito@google.com>