Built in Jiinja filter `difference` does not work in pillar stack module

[asyncmind0]

Description of Issue/Question

Setup

(Please provide relevant configs and/or SLS files (Be sure to remove sensitive info).)

Steps to Reproduce Issue

(Include debug logs if possible and relevant.)
Jan 22 13:32:20 salt0 salt-master[16462]: [ERROR ] Execption caught loading ext_pillar 'stack':
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/salt/pillar/init.py", line 821, in ext_pillar
Jan 22 13:32:20 salt0 salt-master[16462]: key)
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/salt/pillar/init.py", line 764, in _external_pillar_data
Jan 22 13:32:20 salt0 salt-master[16462]: val)
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/salt/pillar/stack.py", line 419, in ext_pillar
Jan 22 13:32:20 salt0 salt-master[16462]: stack = _process_stack_cfg(cfg, stack, minion_id, pillar)
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/salt/pillar/stack.py", line 459, in _process_stack_cfg
Jan 22 13:32:20 salt0 salt-master[16462]: obj = yaml.safe_load(jenv.get_template(unix_path).render(stack=stack))
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/jinja2/environment.py", line 830, in get_template
Jan 22 13:32:20 salt0 salt-master[16462]: return self._load_template(name, self.make_globals(globals))
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/jinja2/environment.py", line 804, in _load_template
Jan 22 13:32:20 salt0 salt-master[16462]: template = self.loader.load(self, name, globals)
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/jinja2/loaders.py", line 125, in load
Jan 22 13:32:20 salt0 salt-master[16462]: code = environment.compile(source, name, filename)
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/jinja2/environment.py", line 591, in compile
Jan 22 13:32:20 salt0 salt-master[16462]: self.handle_exception(exc_info, source_hint=source_hint)
Jan 22 13:32:20 salt0 salt-master[16462]: File "/usr/lib/python2.7/dist-packages/jinja2/environment.py", line 780, in handle_exception
Jan 22 13:32:20 salt0 salt-master[16462]: reraise(exc_type, exc_value, tb)
Jan 22 13:32:20 salt0 salt-master[16462]: File "/opt/salt/srv/stack/roles/prometheus.yml", line 63, in
Jan 22 13:32:20 salt0 salt-master[16462]: {% for node in pillar['hosts'].keys() | difference(exclusions) %}
Jan 22 13:32:20 salt0 salt-master[16462]: [CRITICAL] Pillar render error: Failed to load ext_pillar stack: no filter named 'difference'

Versions Report

(Provided by running salt --versions-report. Please also mention any differences in master/minion versions.)
Salt Version:
Salt: 2017.7.2

Dependency Versions:
cffi: 1.11.4
cherrypy: 3.2.3
dateutil: 2.6.1
docker-py: 1.10.6
gitdb: 2.0.0
gitpython: 2.1.1
ioflo: Not Installed
Jinja2: 2.9.4
libgit2: Not Installed
libnacl: Not Installed
M2Crypto: Not Installed
Mako: Not Installed
msgpack-pure: Not Installed
msgpack-python: 0.4.8
mysql-python: 1.2.3
pycparser: 2.18
pycrypto: 2.6.1
pycryptodome: Not Installed
pygit2: Not Installed
Python: 2.7.13 (default, Nov 24 2017, 17:33:09)
python-gnupg: 0.3.6
PyYAML: 3.12
PyZMQ: 16.0.2
RAET: Not Installed
smmap: 2.0.1
timelib: Not Installed
Tornado: 4.4.3
ZMQ: 4.1.6

System Versions:
dist: debian 9.3
locale: UTF-8
machine: x86_64
release: 4.9.0-5-amd64
system: Linux
version: debian 9.3