Apparently, if I pass an int into argv:

VenvPexProcess(... argv=(..., 42, ...), ...)

I get a big ugly error:

00:31:59.12 [ERROR] panic at 'called `Result::unwrap()` on an `Err` value: "Field `argv` was not convertible to type alloc::vec::Vec<alloc::string::String>: PyErr { ptype: <class \'TypeError\'>, pvalue: Some(\'Expected type that converts to PyString but received int\'), ptraceback: None }"', src/nodes.rs:308
00:31:59.12 [ERROR] Please set RUST_BACKTRACE=1, re-run, and then file a bug at <https://github.com/pantsbuild/pants/issues>.

I ended up grepping to find all the

argv

instances in my code to see what was up.

Hm yeah that's an error from rust-cpython crate. We could add eager validation in Python that everything is a string - only downside is there's a perf hit paid every time, even tho this is only relevant when developing plugins