Specify the minimum required version of pytest

A previous change introduced the usage of pytest.param to our test
suite in commit 7aba0bfc906409073c4d246ec009a8622551726a.

This was only added to pytest 3.1.0, and the tests can't work with older
versions.

1 files changed, 1 insertions, 1 deletions

diff --git a/setup.py b/setup.py
index 6957e7d4e..a7cfc21d1 100755
--- a/setup.py
+++ b/setup.py
@@ -146,5 +146,5 @@ setup(name='BuildStream',
                      'pytest-env',
                      'pytest-pep8',
                      'pytest-cov',
-                     'pytest'],
+                     'pytest >= 3.1.0'],
       zip_safe=False)