Replace atty dependency in slog-term due to RUSTSEC-2021-0145

[willbuckner]

The title says it all, but there is an advisory for atty which is unmaintained, and this dependency likely needs to be replaced with something else. Advisory is here: https://rustsec.org/advisories/RUSTSEC-2021-0145.html

Thanks!

[dpc]

So https://crates.io/crates/is-terminal ?

[Techcable]

Hi! I fixed this in PR slog-rs/term#45

This doesn't look particularly important, so I'm not going to rush an emergency hotfix.

I will release it in the net batch of updates for term when I release v2.9.1.

This will probably come sometime in early December. I have one more week of classes and then finals.

[willbuckner]

Looks great, thanks @Techcable! Looks like tests are failing due to:

Downloaded once_cell v1.16.0
error: failed to parse manifest at `/home/runner/.cargo/registry/src/github.aaakk.us.kg-1ecc6299db9ec823/once_cell-1.16.0/Cargo.toml`

Caused by:
  feature `edition[20](https://github.com/slog-rs/term/actions/runs/3562324356/jobs/5983962221#step:4:21)[21](https://github.com/slog-rs/term/actions/runs/3562324356/jobs/5983962221#step:4:22)` is required

  this Cargo does not support nightly features, but if you
  switch to nightly channel you can add
  `cargo-features = ["edition2021"]` to enable this feature
Error: Process completed with exit code 101.

As far as timeliness, December should be fine, but I will say that projects are having to allowlist this RUSTSEC in cargo-deny/cargo-audit rules until it's fixed. No big deal though, I have a tracking ticket internally to clean up the deny rules once this lands. Our project is not actually vulnerable due to this, it's just making cargo deny complain :)

[sunfishcode]

I added a comment to that PR explaining the test failures.

[gnaaman-dn]

If MSRV is ever raised to 1.70, this dependency can also be dropped in favour for std::io::IsTerminal