Better error messages! Switch the library used for validating configuration files (from pykwalify to jsonschema).

test_requirements.txt

@@ -1,26 +1,21 @@
 appdirs==1.4.4; python_version >= '3.8'
-atomicwrites==1.4.0
 attrs==20.3.0; python_version >= '3.8'
 black==19.10b0; python_version >= '3.8'
 click==7.1.2; python_version >= '3.8'
 colorama==0.4.4
 coverage==5.3
-docopt==0.6.2
 flake8==3.8.4
 flexmock==0.10.4
-isort==5.6.4
+isort==5.9.1
 mccabe==0.6.1
-more-itertools==8.6.0
 pluggy==0.13.1
 pathspec==0.8.1; python_version >= '3.8'
 py==1.10.0
 pycodestyle==2.6.0
 pyflakes==2.2.0
-pykwalify==1.7.0
+jsonschema==3.2.0
 pytest==6.1.2
 pytest-cov==2.10.1
-python-dateutil==2.8.1
-PyYAML==5.4.1
 regex; python_version >= '3.8'
 requests==2.25.0
 ruamel.yaml>0.15.0,<0.18.0