tox does not have a skip_missing_envs setting.

[danieljmv01]

towncrier/tox.ini

Lines 1 to 4 in 27cd970

	[tox]
	envlist = cov-erase, flake8, {pypy27,pypy36,pypy37,py27,py35,py36,py37,py38,py39}-{tests,flake8,check-manifest,check-newsfragment}, cov-report
	isolated_build=true
	skip_missing_envs = true

The setting skip_missing_envs included in the [tox] section of the tox.ini is not a tox setting, at least in the most recent versions of tox.
It is likely that it was confused with [skip_missing_interpreters](https://tox.wiki/en/latest/config.html#conf-skip_missing_interpreters).

[adiroiban]

Most probably.

This was introduced here 4068ee4

there is also #319 which tries to prepare for tox v4.

I am not a big tox fan. I keep it's usage to the minimum.

But I am happy to review and merge any improvement on tox.

[SmileyChris]

We're using nox, not tox now, so this is a non-issue.