🚨 Pin pytest-xdist

Wait for a new pytest-django release, which supports pytest-xdist~=2.0
as per pytest-dev/pytest-django#861

src/setup.py

@@ -143,7 +143,7 @@ def run(self):
             "pytest-mock",
             "pytest-rerunfailures",
             "pytest-sugar",
-            "pytest-xdist",
+            "pytest-xdist<2",  # Wait for a pytest-django newer than 3.9.0
             "pywatchman",
             "responses",
             "urllib3",