Pin tests to pytest < 3
diff --git a/tox.ini b/tox.ini
index 8bceac2..fd5bee2 100644
--- a/tox.ini
+++ b/tox.ini
@@ -5,7 +5,7 @@
     nose
     mock
     nose2: nose2
-    pytest: pytest>=2
+    pytest: pytest>=2,<3
     unit2: unittest2
 commands=
     nose: nosetests