CfT: Test out Rustup's `reqwest` backend with `rustls`

[!NOTE]
rustup v1.28.0 beta is now available for early adopters! See this discussion thread for more info :)

In #3790, we have started an initiative to make reqwest/rustls Rustup's future download/TLS backend combination.

While a maximally-Rust stack might sound exciting, we want to get it tested beforehand to minimize the possibility for you to experience hiccups in production.

If you're using rustup v1.28+, this should be available for you by default [^3] ; for rustup v1.27 and earlier, chances are you can opt in right now by setting the environment variable RUSTUP_USE_RUSTLS=1 [^1] .

Please feel free to share your experiences below, and many thanks in advance 🙇‍♀️

Note

You can report in this issue the changes that switching to rustls has made to your workflow, so I assume most of them are breakages: what worked before but now doesn’t work with rustls.
Of course, it could also be the opposite, i.e. what didn't work but now works.

If you can’t feel any difference, that’s actually a good news for us! Just reacting with 😄[^2] to this message would be perfect in this case :)

Tasks

• https://github.com/rust-lang/rustup/pull/3979

[^1]: Please make sure that RUSTUP_USE_CURL is NOT set, otherwise the curl download backend will be selected; to opt out, just set RUSTUP_USE_RUSTLS=0.
[^2]: GitHub has recently replaced the emoji with 😂, I have no idea why this is the case 🤷‍♀ No, they have changed it back, never mind :)
[^3]: At the time of writing, the only exceptions are powerpc64*, loongarch*, *openbsd* and *illumos*.

Start with rustup v1.28+ and the reqwest/rustls backend described in the issue; check whether your existing download workflow changes. Report anything that worked before but fails, anything newly working, or indicate that you noticed no difference; the listed task is already complete.