In https://github.com/openai/codex/pull/16528, I am trying to get tests
running under Bazel on Windows, but currently I see:
```
thread 'suite::user_shell_cmd::user_shell_command_does_not_set_network_sandbox_env_var' (10220) panicked at core/tests\suite\user_shell_cmd.rs:358:5:
assertion failed: `(left == right)`
Diff < left / right > :
<1
>0
```
This PR updates the `assert_eq!()` to provide more information to help
diagnose the failure.
---
[//]: # (BEGIN SAPLING FOOTER)
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* #16608
* __->__ #16606