enable pytest 5.x and pytest-xdist >= 1.28

Makefile

@@ -26,7 +26,7 @@ MODULE=cwltool
 # `[[` conditional expressions.
 PYSOURCES=$(wildcard ${MODULE}/**.py tests/*.py) setup.py
 DEVPKGS=diff_cover black pylint coverage pep257 pydocstyle flake8 mypy\
-	pytest-xdist==1.27.0 isort wheel -rtest-requirements.txt
+	pytest-xdist isort wheel -rtest-requirements.txt
 DEBDEVPKGS=pep8 python-autopep8 pylint python-coverage pydocstyle sloccount \
 	   python-flake8 python-mock shellcheck
 VERSION=3.0.$(shell TZ=UTC git log --first-parent --max-count=1 \

appveyor.yml

@@ -28,7 +28,7 @@ install:
   - ps: 'Install-Product node 0.12 x64'
   - "set PATH=%PYTHON%\\Scripts;%PATH%"
   - "%PYTHON%\\python.exe -m pip install -U pip setuptools^>=20.3 wheel"
-  - "%PYTHON%\\python.exe -m pip install -U codecov -rtest-requirements.txt pytest-xdist==1.27 "
+  - "%PYTHON%\\python.exe -m pip install -U codecov -rtest-requirements.txt pytest-xdist"
     # Note the use of a `^` to escape the `>`
 
 build_script:

test-requirements.txt

@@ -1,4 +1,4 @@
-pytest < 4.3.0
+pytest < 6
 mock >= 2.0.0
 pytest-mock >= 1.10.0
 pytest-cov

tox.ini

@@ -32,7 +32,7 @@ passenv =
 deps =
   -rrequirements.txt
   py{35,36,37,38}-unit: codecov
-  py{35,36,37,38}-unit: pytest-xdist<1.28.0
+  py{35,36,37,38}-unit: pytest-xdist
   py{35,36,37,38}-unit: pytest-cov
   py{35,36,37,38}-{unit,mypy}: -rtest-requirements.txt
   py{35,36,37,38}-unit: galaxy-tool-util