Update toxfile with better optimized settings and task dist

Fix pycache cleanup in makefile
Update makefile to use tox doc env for building documentation

tox.ini

@@ -1,9 +1,10 @@
 [tox]
-envlist = py37, py36, lint, typing, security, docs
+envlist = py36, py37, py38, format, static, docs
+skip_missing_interpreters = true
 isolated_build = true
 
 [testenv]
-description = Run the unit tests (pytest)
+description = Run unit tests (pytest+{basepython})
 deps =
     marshmallow == 3.5.0
     passlib == 1.7.2
@@ -14,32 +15,30 @@ deps =
 commands =
     pytest --cov={envsitepackagesdir}/keyosk --cov-config .coveragerc tests/ --cov-report term-missing
 
-[testenv:lint]
-description = Check code formatting against black and pylint
+[testenv:format]
+description = Enforce code formatting (pre-commit)
+skip_install = true
 deps =
     pre-commit == 2.1.0
-    pylint == 2.3.1
-    astroid == 2.2.5
 commands =
     pre-commit run --all-files
-    pylint keyosk
 
-[testenv:typing]
-description = Check type annotations with mypy
+[testenv:static]
+description = Static code analysis (mypy+pylint+bandit)
+skip_install = true
+ignore_errors = true
 deps =
+    pylint == 2.3.1
+    astroid == 2.2.5
     mypy == 0.761
-commands =
-    mypy keyosk --ignore-missing-imports --no-strict-optional
-
-[testenv:security]
-description = Check security vulnerabilities (bandit)
-deps =
     bandit == 1.6.2
 commands =
+    mypy keyosk --ignore-missing-imports --no-strict-optional
+    pylint keyosk --rcfile .pylintrc
     bandit --recursive keyosk
 
 [testenv:docs]
-description = Build documentation to check RST syntax (sphinx)
+description = Build documentation (sphinx)
 deps =
     sphinx == 2.4.2
     sphinx-autodoc-typehints == 1.10.3