the new keyword async is causing errors when we run this with python 3.8.
https://docs.python.org/3/whatsnew/3.7.html

I tried in the first place, to change the definition of that value in the place where the context is defined, but it seems that it is taken from https://github.com/jazzband/django-pipeline,

This solves many problems for lms and cms tests that were making the jenkins workers get timeout.

That template have not seen changed since 2012, so I had to do additional changes in the templates in order to pass the xsslint checks:

mako-missing-default
mako-invalid-html-filter

I am not sure about the remove of the safe filter.

But I didn't found information about the 'safe' filter. It is probably that the now default 'h' filter is enough.