add jinja2.ext.do extension to Jinja environment

src/opnsense/service/modules/template.py

@@ -56,7 +56,8 @@ class Template(object):
 
         # setup jinja2 environment
         self._template_dir = os.path.dirname(os.path.abspath(__file__))+'/../templates/'
-        self._j2_env = jinja2.Environment(loader=jinja2.FileSystemLoader(self._template_dir), trim_blocks=True)
+        self._j2_env = jinja2.Environment(loader=jinja2.FileSystemLoader(self._template_dir), trim_blocks=True,
+                                          extensions=["jinja2.ext.do",])
 
     def _readManifest(self, filename):
         """