[Pkg-rust-maintainers] Bug#1063601: tailspin: FTBFS: error[E0407]: method `backtrace` is not a member of trait `Error`

[Peter Green]

reassign 1063601 tailspin 3.0.0+dfsg-1
retitle 1063601 tailspin FTBFS error: environment variable `CARGO_CHANNEL` not defined at compile time
thanks

 >> [eyre 0.6.8] error[E0407]: method `backtrace` is not a member of trait `Error`
 >> [eyre 0.6.8]   --> /<<PKGBUILDDIR>>/target/x86_64-unknown-linux-gnu/release/build/eyre-eb1eb971e427fb49/out/probe.rs:19:9
> The above seems like a failure not in tailspin but in librust-eyre-dev.

I don't think the errors Sebastian quoted are the cause of the build failure
at all. I think they are just noise from a test compilation performed to
determine what the compiler supports. Those same errors are present
in the successful build log for tailspin 2.0.0

The actual error seems to be.

> error: environment variable `CARGO_CHANNEL` not defined at compile time
>   --> tests/utils.rs:11:48
>    |
> 11 |     PathBuf::from(format!("./target/{}/tspin", env!("CARGO_CHANNEL")))
>    |                                                ^^^^^^^^^^^^^^^^^^^^^
>    |
>    = help: Cargo sets build script variables at run time. Use `std::env::var("CARGO_CHANNEL")` instead
>    = note: this error originates in the macro `env` (in Nightly builds, run with -Z macro-backtrace for more info)

I also notice the following earlier in the build log.

> "debian cargo wrapper: WARNING: falling back to simply calling upstream cargo, because CARGO_HOME does not end with debian/cargo_home:"

This message appears in the failed logs for 3.0.0 but not in the succesful logs
for 2.0.0.

After serching for CARGO_CHANNEL I think may be the actual cause of the failure.
All the results on codesearch.debian.net for CARGO_CHANNEL seem to relate to dh_cargo
or your fork thereof. So I think these are probablly related.