build: run pylint as part of lint task

Pylint analyses the code for common bugs.

Fixes: GREG-16

Makefile

@@ -2,6 +2,7 @@ BLACK ?= black -q
 MYPY ?= mypy
 PIP ?= pip -q
 POETRY ?= poetry
+PYLINT ?= pylint -sn
 PYTHON ?= python3.9
 VENV ?= venv
 
@@ -34,6 +35,7 @@ test: $(VENV)
 .PHONY: lint
 lint: $(VENV)
 	$(venv) $(poetry) -q check
+	$(venv) $(PYLINT) $(PACKAGES)
 	$(venv) $(BLACK) --check --diff $(PACKAGES)
 
 .PHONY: fmt