fixed some NameErrors

--HG--
branch : trunk
diff --git a/jinja2/ext.py b/jinja2/ext.py
index 5ae317d..1158505 100644
--- a/jinja2/ext.py
+++ b/jinja2/ext.py
@@ -15,7 +15,7 @@
 from jinja2.environment import get_spontaneous_environment
 from jinja2.runtime import Undefined, concat
 from jinja2.parser import statement_end_tokens
-from jinja2.exceptions import TemplateAssertionError
+from jinja2.exceptions import TemplateAssertionError, TemplateSyntaxError
 from jinja2.utils import import_string, Markup