Jinja2 is a template engine written in pure Python.  It provides a
Django inspired non-XML syntax but supports inline expressions and
an optional sandboxed  environment.

Circular dependencies warning: The DOCS=yes flag needs the optional
dependency Sphinx, which needs Jinja2, which needs Sphinx because
DOCS=yes ... So...  If you really need the docs, build Jinja2
without the DOCS=yes flag, build Sphinx, then rebuild Jinja2 with
DOCS=yes.  Incidentally, unless you are a developer, you don't
normally need the DOCS=yes flag.