pydbus: Add ebuild from upstream

Add pydbus from upstream and modify keyword + python_compat for
Chromium.

BUG=b:211516498
TEST=emerge-zork pydbus passes

Change-Id: I01c232ebb1d6944f69a10ef38f25d53d0c37ac2c
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/3379004
Tested-by: Abhishek Pandit-Subedi <abhishekpandit@google.com>
Reviewed-by: Jack Rosenthal <jrosenth@chromium.org>
Commit-Queue: Abhishek Pandit-Subedi <abhishekpandit@google.com>
4 files changed