Issue 2178 - [cms] Allow using {% do %} in Jinja2 templates

cms/converters.py

 # coding: utf-8
 
 # This file is part of the Adblock Plus web scripts,
 # Copyright (C) 2006-2015 Eyeo GmbH
 #
 # Adblock Plus is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License version 3 as
 # published by the Free Software Foundation.
 #
 # Adblock Plus is distributed in the hope that it will be useful,
@@ skipping 266 matching lines @@
       code = self._params["source"].read_file(path)
       module = imp.new_module(root.replace("/", "."))
       exec code in module.__dict__
 
       func = os.path.basename(root)
       if not hasattr(module, func):
         raise Exception("Expected function %s not found in filter file %s" % (func, filename))
       filters[func] = getattr(module, func)
       filters[func].module_ref = module  # Prevent garbage collection
 
-    self._env = jinja2.Environment(loader=self._SourceLoader(self._params["source"]), autoescape=True)
+    self._env = jinja2.Environment(
+        loader=self._SourceLoader(self._params["source"]),
+        extensions=["jinja2.ext.do",],
+        autoescape=True
+    )
     self._env.filters.update(filters)
     self._env.globals.update(globals)
 
   def get_html(self, source):
     template = self._env.from_string(source)
     return template.render(self._params)
 
   def translate(self, default, name, comment=None):
     # Note: We currently ignore the comment, it is only relevant when
     # generating the master translation.
@@ skipping 34 matching lines @@
         stack.pop()
       stack[-1]["subitems"].append(item)
       stack.append(item)
     return structured
 
 converters = {
   "html": RawConverter,
   "md": MarkdownConverter,
   "tmpl": TemplateConverter,
 }