Delay logging about missing certifi until it is really needed.
Delay logging about missing certifi until it is really needed.

Logging during module import time is not cool, it causes logger to auto
configure itself with some (wrong) defaults.

It eventually triggers assert in logging_utilities.prepare_logging (that gets
confused because the logger is already configured).

R=maruel@chromium.org, iannucci@chromium.org, aludwin@google.com
BUG=

Review-Url: https://codereview.chromium.org/2976073002

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py