[Fixed]-Python HTML to PDF with full support for CSS3 and HTML5

You should check weasyprint, It supports most of the CSS3 and HTML5, at the moment it doesn’t support flex-wrap: wrap propierties as far as I know.

I used xhtml2pdf with Reportlab it supports some CSS3 (supports HTML5 CSS 2.1). I don’t recommend it when you have a better and simple tool like weasyprint.

Simple Django Tutorial with weasyprint

If you or someone else is still looking for some solutions, check out this:
Render HTML to PDF in Django site

also
https://github.com/chrisglass/xhtml2pdf
or
https://github.com/JazzCore/python-pdfkit

I hope this will help most of you.