dev-python/pyudev: Replace python_gen_usedep with python_gen_cond_dep

An upgrade attempt was made in CL:2329159, but it fails because of
reverse depedencies that want python 2* support.

BUG=chromium:1111336
TEST=emerge pyudev

Change-Id: Ia1d198bab7f72744fa8ba70050e05ce9c530a9cb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/portage-stable/+/2333114
Tested-by: Allen Webb <allenwebb@google.com>
Auto-Submit: Allen Webb <allenwebb@google.com>
Commit-Queue: Allen Webb <allenwebb@google.com>
Commit-Queue: Alex Klein <saklein@chromium.org>
Reviewed-by: Alex Klein <saklein@chromium.org>
2 files changed