Function progress_bar 

pub fn progress_bar(len: u64, message: &str) -> ProgressBar

Create a styled progress bar with len steps and an initial message.

The bar uses the format:

⠙ [████████████░░░░░░░░░░░░░░░░░░░░░░░░░░░░] 12/50 Processing KEY

The caller is responsible for calling ProgressBar::inc and ProgressBar::finish_with_message when done.