Run CI tests against the latest pytest 3.x release automatically. (#421)

Author: pelme

tox.ini

@@ -13,6 +13,7 @@ envlist =
 [testenv]
 deps =
     django-configurations==1.0
+    pytest-xdist==1.15
 
     checkqa: flake8
 
@@ -27,10 +28,8 @@ deps =
 
     postgres: psycopg2
 
-    pytest29: pytest==2.9.2
-    pytest29: pytest-xdist==1.15
-    pytest30: pytest==3.0.3
-    pytest30: pytest-xdist==1.15
+    pytest29: pytest>=2.9,<3.0
+    pytest30: pytest>=3.0,<3.1
 
 setenv =
      PYTHONPATH = {toxinidir}:{env:PYTHONPATH:}