Julia variable assignment in `@pywith`

Is it (or should it) be possible to assign values to Julia variables within an `@pywith` block? For example,
```julia
julia> @pywith pybuiltin("open")("Manifest.toml", "r") as f begin
manifest = f.readlines()
end

julia> manifest
ERROR: UndefVarError: manifest not defined

```

Thanks!

Start by reading the implementation of the @pywith macro and reproducing the shown example with pybuiltin("open") and Manifest.toml. Determine how assignment inside the block is scoped, then define and test the expected behavior for accessing manifest after the block; the issue does not name a source file or test.

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