Configure black, isort, pylint and bandit in CI

- Add 'lint' tox environment that runs black, isort and bandit, and
  mypy (moved from its own env).
- Run new tox env in ci GitHub Action.

Signed-off-by: Lukas Puehringer <[email protected]>

.github/workflows/ci.yml

@@ -27,7 +27,7 @@ jobs:
             toxenv: py38-no-gpg
           - python-version: 3.8
             os: ubuntu-latest
-            toxenv: mypy
+            toxenv: lint
 
     runs-on: ${{ matrix.os }}
 

tox.ini

@@ -4,7 +4,7 @@
 # and then run "tox" from this directory.
 
 [tox]
-envlist = mypy, py37, py38, py39, py310, purepy38, py38-no-gpg, py38-test-gpg-fails
+envlist = lint, py37, py38, py39, py310, purepy38, py38-no-gpg, py38-test-gpg-fails
 skipsdist = True
 
 [testenv]
@@ -21,7 +21,7 @@ commands =
     coverage report -m --fail-under 97
 
 [testenv:purepy38]
-deps = 
+deps =
 
 commands =
     python -m tests.check_gpg_available
@@ -41,6 +41,13 @@ setenv =
 commands =
     python -c "import securesystemslib.gpg.constants"
 
-[testenv:mypy]
+[testenv:lint]
 commands =
+    # TODO: Move configs to pyproject.toml
+    black --check --diff --line-length=80 --extend-exclude=_vendor  .
+    isort --check --diff --line-length=80 --extend-skip-glob='*/_vendor/*' \
+                                          --profile=black --project=securesystemslib .
+
+    pylint -j 0 --rcfile=pylintrc securesystemslib tests
+    bandit --recursive securesystemslib --exclude _vendor
     mypy