WeasyPrint doesn't support some of the CSS3 features (yet, I hope), and running a Python script throws a long list of ignored entries (eg. box shadows, gradients), then a job summary. Is it possible to run WeasyPrint in silent mode, without any information shown?
According to the documentation, you can create a new logger object to override WeasyPrint default behavior. The following code snippet is taken from the documentation page itself.
import logging
logger = logging.getLogger('weasyprint')
logger.handlers = [] # Remove the default stderr handler
logger.addHandler(logging.FileHandler('/path/to/weasyprint.log'))
If you don't want any logging at all, you can remove the last line.