No color on `--style progress`

[DrSensor]

I just notice the color output are disabled on error when using --style progress while basic and steps works just fine.

// number.rs
extern "C" { static mut offset: u32; }
fn add() -> u32 { offset }

-- Knitfile
return b{
  $ %.wasm: %.rs
    rustc --target=wasm32-unknown-unknown --crate-type=lib $input -o $output    
}