pytest-xdist is required by now

.travis.sh

@@ -38,7 +38,7 @@ if [ "$1" == "translation-spelling" ]; then
 	potypo
 fi
 if [ "$1" == "tests" ]; then
-	pip3 install -r src/requirements.txt -Ur src/requirements/dev.txt pytest-xdist
+	pip3 install -r src/requirements.txt -Ur src/requirements/dev.txt
 	cd src
 	python manage.py check
 	make all compress

src/requirements/dev.txt

@@ -9,6 +9,7 @@ codecov
 coverage
 pytest==3.6.*
 pytest-django
+pytest-xdist
 isort
 pytest-rerunfailures==4.*
 pytest-mock==1.6.*