feat for issue #809: impl std::error::Error for cursive::theme::Error

[chet]

#809 had been opened inquiring about implementing std::error::Error for cursive::theme::Error so they could do something like this:

fn load_theme(siv: &mut CursiveRunnable, path: PathBuf) -> anyhow::Result<()> {
    siv.load_theme_file(path)?;
    Ok(())
}

Instead of having to do this:

fn load_theme(siv: &mut CursiveRunnable, path: PathBuf) -> anyhow::Result<()> {
    match siv.load_theme_file(path) {
        Ok(_) => Ok(()),
        Err(e) => match e {
            cursive::theme::Error::Io(e) => Err(e.into()),
            cursive::theme::Error::Parse(e) => Err(e.into()),
        }
    }
}

It seemed like low hanging fruit, so I figured I'd offer up a PR. Included some tests for the different Error::Io, Error::Parse and ? cases.

Thank you for considering this change!

[chet]

cc @septante

[septante]

I ended up switching to ratatui because I needed support for rendering images, but this looks like what I was asking for. Thank you!

[chet]

Ahh nice @septante! And you're welcome! Better late than never, haha!

[gyscos]

Thanks for the PR!

[chet]

@gyscos Of course! I'll try to look through the Issues list and see if I can grab a few more of them over the next few weeks.