Downgrade pytest to a version below 3.3 since the new log capture feature breaks our tests.

Omer Katz · Omer Katz · commit acf850643d0c · 2017-12-05T16:42:34.000+02:00
diff --git a/requirements/test.txt b/requirements/test.txt
@@ -1,2 +1,2 @@
 case>=1.3.1
-pytest>=3.0
+pytest>=3.0,<3.3
