how to fix the error: "jinja2.exceptions.TemplateAssertionError: no filter named 'rejectattr' "??

[luckypoem]

hello.

(dev) root@localhost:/usr/local/wok-site# hg clone https://bitbucket.org/sourcemage/website sourcemage.org
(dev) root@localhost:/usr/local/wok-site# cd sourcemage.org
(dev) root@localhost:/usr/local/wok-site/sourcemage.org# cd news
(dev) root@localhost:/usr/local/wok-site/sourcemage.org/news# wok
WARNING:root:Textile not enabled.
Traceback (most recent call last):
File "/root/dev/bin/wok", line 4, in
import('pkg_resources').run_script('wok==1.1.1', 'wok')
File "/root/dev/local/lib/python2.7/site-packages/pkg_resources/init.py", line 738, in run_script
self.require(requires)[0].run_script(script_name, ns)
File "/root/dev/local/lib/python2.7/site-packages/pkg_resources/init.py", line 1506, in run_script
exec(script_code, namespace, namespace)
File "/root/dev/lib/python2.7/site-packages/wok-1.1.1-py2.7.egg/EGG-INFO/scripts/wok", line 4, in
import('pkg_resources').run_script('wok==1.1.1', 'wok')
File "build/bdist.linux-x86_64/egg/wok/engine.py", line 152, in init
File "build/bdist.linux-x86_64/egg/wok/engine.py", line 190, in generate_site
File "build/bdist.linux-x86_64/egg/wok/engine.py", line 376, in load_pages
File "build/bdist.linux-x86_64/egg/wok/page.py", line 117, in from_file
File "build/bdist.linux-x86_64/egg/wok/page.py", line 275, in build_meta
File "/root/dev/lib/python2.7/site-packages/Jinja2-2.6-py2.7.egg/jinja2/environment.py", line 719, in get_template
return self._load_template(name, self.make_globals(globals))
File "/root/dev/lib/python2.7/site-packages/Jinja2-2.6-py2.7.egg/jinja2/environment.py", line 693, in _load_template
template = self.loader.load(self, name, globals)
File "/root/dev/lib/python2.7/site-packages/Jinja2-2.6-py2.7.egg/jinja2/loaders.py", line 127, in load
code = environment.compile(source, name, filename)
File "/root/dev/lib/python2.7/site-packages/Jinja2-2.6-py2.7.egg/jinja2/environment.py", line 493, in compile
self.handle_exception(exc_info, source_hint=source)
File "templates/rss.html", line 6, in template
{{ (site.pages | rejectattr("meta.date", "none") | sort(true, attribute='meta.date') | first).meta.date }}
jinja2.exceptions.TemplateAssertionError: no filter named 'rejectattr'
(dev) root@localhost:/usr/local/wok-site/sourcemage.org/news#

thank u