edx-platform/common/test/test_microsites/test_microsite/templates/head-extra.html

<%namespace name='static' file='../../static_content.html'/>
<%! from microsite_configuration import microsite %>
<% style_overrides_file = microsite.get_value('css_overrides_file') %>

% if style_overrides_file:
  <link rel="stylesheet" type="text/css" href="${static.url(style_overrides_file)}" />
% endif