Start enforcing ruff rules

pyproject.toml

@@ -5,3 +5,29 @@ requires = [
     "cython"
 ]
 build-backend = "setuptools.build_meta"
+
+[tool.ruff]
+target-version = "py38"
+
+[tool.ruff.lint]
+extend-select = [
+    "UP",   # pyupgrade
+    "C4",   # flake8-comprehensions
+    "PIE",  # flake8-pie
+    "FLY",  # flynt
+    "PERF", # Perflint
+    "RUF",
+]
+ignore = [
+    "F841",    # Local variable is assigned to but never used
+    "UP031",   # Use format specifiers instead of percent format
+    "UP032",   # Use f-string instead of `format` call
+    "PERF203", # `try`-`except` within a loop incurs performance overhead
+    "RUF003",
+    "RUF005",  # Consider iterable unpacking instead of concatenation
+    "RUF012",  # Mutable class attributes should be annotated with `typing.ClassVar`
+    "RUF100",  # Unused `noqa` directive
+]
+
+[tool.ruff.lint.extend-per-file-ignores]
+"**/__init__.py" = ["F401"]  # imported but unused