Rinohtype/Spinx - How to use python variables in stylesheet

Question

I use sphinx to generate HTML and PDF documentation, and was using latex until now to generate PDF, but now looking at swapping for rinohtype.

I'm looking at setting up some custom headers and footers, but would like to include variable text into them, for the version number for example, which comes from a sphinx python plugin. I have rst substitutions, for example |version|, that I use in various places in the document, but if I add it to the header via a stylesheet it doesn't get substituted. I also have python variables, for example version, in my conf.py so I also tried to use {version} in my stylesheet, but the builder complains that the variable doesn't exists.

FYI, here is how I tried to define my header :

[contents_page]
header_text = '|document_id| |version| |shortdate|' (header)

[contents_page]
header_text = '{document_id} {version} {shortdate}' (header)

Any idea how to get around that issue ?

Thanks