1. virtualenv field in the spec is ignored.
2. --vpython-tool removed support for delete and help subcommands.
3. --vpython-tool installed removed support for naming venv.
4. removed support for -vpython-interpreter.
5. removed support for searching interpreters in host PATH.
6. python 2.7 is available only if the binary is invoked as `vpython`.
7. fixed a bug that passes invalid vpython arguments to the script,
which may be silently ignored.
8. python_version in the vpython_spec must specify a minor version
(python_version: "3" is not valid anymore).
9. vpython now requires the cipd binary to be present in PATH, which is
true already when using Swarming or depot_tools.
Also updates the LUCI_OWNERS to add peep-software-deploy team.
Bug:1415212
Change-Id: I295c1aad1516a0c36eefa2ae04e85cabb518bda8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/4653897
Reviewed-by: Robbie Iannucci <iannucci@chromium.org>
Commit-Queue: Chenlin Fan <fancl@chromium.org>