add import_exception_bound! macro

[davidhewitt]

For #3989

The idea here is that this macro implements only the traits needed to use an imported exception inside a Bound (and not as a GIL Ref). This should help with coverage.

cc @alex - want to give this a try?

[alex]

I think there's a syntax error or something somewhere:

   Compiling cryptography-rust v0.1.0 (/Users/alex_gaynor/projects/cryptography/src/rust)
error: expected one of `!` or `[`, found `module`
   --> src/exceptions.rs:26:1
    |
26  | pyo3::import_exception_bound!(cryptography.exceptions, AlreadyUpdated);
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected one of `!` or `[`
    |
   ::: /Users/alex_gaynor/.cargo/git/checkouts/pyo3-8f6c8fc902a366fa/33371a4/src/types/mod.rs:233:34
    |
233 |     ($name:ty, $typeobject:expr, $module:expr $(, #checkfunction=$checkfunction:path)? $(;$generics:ident)*) => {
    |                                  ------------ while parsing argument for this `expr` macro fragment
    |
    = note: this error originates in the macro `pyo3::import_exception_bound` (in Nightly builds, run with -Z macro-backtrace for more info)

[davidhewitt]

Ugh, sorry, force-pushed and actually moved some tests over to it now 🤦

[alex]

Ok, local check looks good, pushing to CI for coverage.

[alex]

Yeah, looks green pyca/cryptography#10671

[davidhewitt]

Great!

[codspeed-hq]

CodSpeed Performance Report

Merging #4027 will improve performances by 24.29%

_{Comparing davidhewitt:import-exception (5ce07c3) with main (22e8dd1)}

Summary

⚡ 1 improvements
✅ 71 untouched benchmarks

Benchmarks breakdown

	Benchmark	main	davidhewitt:import-exception	Change
⚡	drop_many_objects	68.6 µs	55.2 µs	+24.29%