Update tox.ini from template

tox.ini

 [tox]
 skipsdist = True
 skip_missing_interpreters = true
-envlist = py37,py38
+envlist = py37,py38,py39
 
 [testenv]
 whitelist_externals = poetry
@@ -22,9 +22,9 @@ setenv =
 
 [testenv:lint]
 commands =
-    - poetry run black --check --diff aleksis/ --exclude "migrations"
-    - poetry run isort -c --diff --stdout -rc -s migrations aleksis/
-    - poetry run flake8 {posargs} --exclude-from-doctest migrations aleksis/
+    poetry run black --check --diff aleksis/
+    poetry run isort -c --diff --stdout aleksis/
+    poetry run flake8 {posargs} aleksis/
 
 [testenv:security]
 commands =
@@ -40,7 +40,7 @@ commands = poetry run make -C docs/ html {posargs}
 
 [testenv:reformat]
 commands =
-    poetry run isort -rc aleksis/
+    poetry run isort aleksis/
     poetry run black aleksis/
 
 [flake8]
@@ -52,10 +52,10 @@ ignore = BLK100,E203,E231,W503,D100,D101,D102,D103,D104,D105,D106,D107,RST215,RS
 line_length = 100
 multi_line_output = 3
 include_trailing_comma = 1
-use_parantheses = 1
 default_section = THIRDPARTY
 known_first_party = aleksis
 known_django = django
+skip = migrations
 sections = FUTURE,STDLIB,DJANGO,THIRDPARTY,FIRSTPARTY,LOCALFOLDER
 
 [mypy]