default_user() via whoami

[zlobober]

ytsaurus-spyt/spyt-package/src/main/python/spyt/utils.py

Lines 221 to 222 in 67b38d8

	def default_user():
	return os.getenv("YT_USER") or getpass.getuser()

Sometimes, local username on user's personal computer may not match the username from YT's perspective. Let's instead perform a whoami call here?

https://github.com/ytsaurus/ytsaurus/blob/a339aeb25afd7ae78fd7fdf5934263951cb19407/yt/python/yt/wrapper/http_helpers.py#L705-L738