Warning triggered from attr 19.2.0 `cmp` usage

[johnthagen]

pytest==5.2.0
attrs==19.2.0 (released 2 hours ago)

GLOB sdist-make: /home/gitlab-runner/builds/DwvLisya/0/setup.py
py36 create: /home/gitlab-runner/builds/DwvLisya/0/.tox/py36
py36 installdeps: -r/home/gitlab-runner/builds/DwvLisya/0/dev-requirements.txt
py36 inst: /home/gitlab-runner/builds/DwvLisya/0/.tox/dist/matlab_server-0.5.0.zip
py36 installed: atomicwrites==1.3.0,attrs==19.2.0,certifi==2019.9.11,chardet==3.0.4,Click==7.0,coverage==4.5.4,entrypoints==0.3,flake8==3.7.8,flake8-import-order==0.18.1,flake8-polyfill==1.0.2,flake8-quotes==2.1.0,Flask==1.1.1,idna==2.8,importlib-metadata==0.23,itsdangerous==1.1.0,Jinja2==2.10.1,jsonschema==3.0.2,MarkupSafe==1.1.1,matlab-server==0.5.0,mccabe==0.6.1,more-itertools==7.2.0,mypy==0.730,mypy-extensions==0.4.1,packaging==19.2,pep8-naming==0.8.2,pkg-resources==0.0.0,pluggy==0.13.0,py==1.8.0,pycodestyle==2.5.0,pyflakes==2.1.1,pyparsing==2.4.2,pyrsistent==0.15.4,pytest==5.2.0,pytest-cov==2.7.1,requests==2.22.0,six==1.12.0,typed-ast==1.4.0,typing-extensions==3.7.4,urllib3==1.25.6,wcwidth==0.1.7,Werkzeug==0.16.0,zipp==0.6.0
py36 runtests: PYTHONHASHSEED='1351706944'
py36 runtests: commands[0] | python -bb -Werror -Wignore:::_pytest.assertion.rewrite -Wignore:::_pytest.tmpdir -Wignore:::site -m pytest --cov=matlab_server --cov-report=html
 File "/home/gitlab-runner/builds/DwvLisya/0/.tox/py36/lib/python3.6/site-packages/_pytest/mark/structures.py", line 370, in <module>
    @attr.s(cmp=False, hash=False)
  File "/home/gitlab-runner/builds/DwvLisya/0/.tox/py36/lib/python3.6/site-packages/attr/_make.py", line 944, in attrs
    eq, order = _determine_eq_order(cmp, eq, order)
  File "/home/gitlab-runner/builds/DwvLisya/0/.tox/py36/lib/python3.6/site-packages/attr/_make.py", line 750, in _determine_eq_order
    warnings.warn(_CMP_DEPRECATION, DeprecationWarning, stacklevel=3)
DeprecationWarning: The usage of `cmp` is deprecated and will be removed on or after 2021-06-01.  Please use `eq` and `order` instead.

Relate to #4507 #4510

[RonnyPfannschmidt]

to make supporting this easier attrs also pushed out a mechanism for backward compat checks so we dont have to pull up version requirements too harshly

[hynek]

Got almost a fix ready for you, give me 10 mins.