A basic extension that parses the RST as a jinja template before rendering as RST

gistfile1.py

def on_source_read(app, docname, source):
    src = source[0]
    if hasattr(app.builder, 'globalcontext'):
        app.info('Using global context')
        source[0] = app.builder.templates.render_string(src, app.builder.globalcontext)
    else:
        source[0] = app.builder.templates.render_string(src, {})


def setup(app):
    app.connect("source-read", on_source_read)