tox: stick to pytest 3.2.5

Newer pytest versions (>=3.3.) require new versions of PythonSix
(>=1.10.0).

We want to keep the current PythonSix version required by piglit.

So let's keep using a pytest version that doesn't force us to increase
PythonSix.

Reviewed-by: Andres Gomez <agomez@igalia.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/tox.ini b/tox.ini
index c1b7a0104..12e8abd9f 100644
--- a/tox.ini
+++ b/tox.ini
@@ -20,7 +20,7 @@ deps =
     py27-accel-nix: backports.lzma
     py27-accel-nix: subprocess32
     py{35,36}: mako==1.0.2
-    pytest>=3.0.3
+    pytest==3.2.5
     pytest-mock
     pytest-pythonpath
     pytest-raises