Generate an HTML file for visualizing all styles defined in a CSS stylesheet.

The script requires the cssutils module which can be installed with:

pip3 install cssutils

python3 css_stylesheet_preview_generator.py stylesheet.css -o preview.html

## verbose mode
python3 css_stylesheet_preview_generator.py stylesheet.css -v -o preview.html

If no output file is specified then HTML is written to stdout. Debug info goes to stderr.