Remove unused imports
diff --git a/jinja2/ext.py b/jinja2/ext.py
index 0652a34..495e643 100644
--- a/jinja2/ext.py
+++ b/jinja2/ext.py
@@ -10,11 +10,10 @@
:copyright: (c) 2010 by the Jinja Team.
:license: BSD.
"""
-from collections import deque
from jinja2 import nodes
from jinja2.defaults import *
from jinja2.environment import Environment
-from jinja2.runtime import Undefined, concat
+from jinja2.runtime import concat
from jinja2.exceptions import TemplateAssertionError, TemplateSyntaxError
from jinja2.utils import contextfunction, import_string, Markup
import six