Downgrade pytest-xdist
It needs an up to date version of pytest
which breaks some tests
@@ -8,7 +8,8 @@ pytest==4.1.1 # pyup: <4.2
# probably a bug related to overriding django settings in
# previous tests
pytest-django==3.4.6 # pyup: <3.4.7
-pytest-xdist==1.28.0
+# pytest-xdist >1.27 requires pytest >4.1
+pytest-xdist==1.27.0
pytest-cov==2.6.1
apipkg==1.5
execnet==1.6.0
