binarytree._populate: suppress PORTAGE_SSH_OPTS KeyError (bug 572494)

Use the "get" method to avoid triggering a KeyError message.

Fixes: 39d81c514c33 ("[...]config.__getitem__(): Partially drop backward compatibility for nonexistent keys.")
X-Gentoo-Bug: 572494
X-Gentoo-Bug-url: https://bugs.gentoo.org/show_bug.cgi?id=572494
(cherry picked from commit 90e142b8fccba0507687b747478c5e060effcb00)

BUG=chromium:462099
TEST=updating sdk binpkgs doesn't throw errors

Change-Id: Ie5c302604606093572a8df6536bc7b7cee3fb659
Reviewed-on: https://chromium-review.googlesource.com/830293
Commit-Ready: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Chirantan Ekbote <chirantan@chromium.org>
1 file changed