Remove use of check_output (not in Py2.6)

tests/versioning/tests.py

@@ -14,13 +14,22 @@ def has_git_requirements():
     return os.path.exists(os.path.join(settings.PROJECT_ROOT, '.git', 'refs', 'heads', 'master'))
 
 
+# Python 2.6 does not contain subprocess.check_output
+def check_output(cmd, **kwargs):
+    return subprocess.Popen(
+        cmd,
+        stdout=subprocess.PIPE,
+        **kwargs
+    ).communicate()[0]
+
+
 @pytest.mark.skipif('not has_git_requirements()')
 def test_fetch_git_sha():
     result = fetch_git_sha(settings.PROJECT_ROOT)
     assert result is not None
     assert len(result) == 40
     assert isinstance(result, six.string_types)
-    assert result == subprocess.check_output(
+    assert result == check_output(
         'git rev-parse --verify HEAD', shell=True, cwd=settings.PROJECT_ROOT
     ).decode('latin1').strip()