Stroke width of confidence bars

I want to have thicker confidence intervals in a bar graph. The documentation specifies how to change the color but I can't find anything else to change the style of the confidence intervals
http://www.pygal.org/en/stable/documentation/configuration/value.html

Start with the configuration documentation at http://www.pygal.org/en/stable/documentation/configuration/value.html and trace how confidence intervals are styled in bar graphs. Confirm how color styling is currently configured, then identify the configuration and documentation changes needed for stroke width; done means users can control and understand the confidence-interval thickness.

Written by the indexing model from the issue text.