Remove deprecation warning and enable some linting rules

tox.ini

@@ -11,8 +11,6 @@ skipsdist = True
 
 [testenv]
 sitepackages = True
-setenv =
-    PYTHONWARNINGS = all
 deps =
     -r{toxinidir}/requirements.txt
     coverage
@@ -34,8 +32,7 @@ commands =
     flake8 apps/activity apps/api apps/logs apps/member apps/note apps/permission apps/treasury apps/wei
 
 [flake8]
-# Ignore too many errors, should be reduced in the future
-ignore = D203, W503, E203, I100, I101, C901
+ignore = I100, I101
 exclude =
     .tox,
     .git,