Enable Pyflakes "F"

ruff.toml

@@ -8,10 +8,8 @@ line-length = 88
 indent-width = 4
 
 [lint]
-# Enable Pyflakes (`F`) and a subset of the pycodestyle (`E`)  codes by default.
-# Unlike Flake8, Ruff doesn't enable pycodestyle warnings (`W`) or
-# McCabe complexity (`C901`) by default.
-select = ["E", "I"]
+# Enable Pyflakes (`F`), pycodestyle (`E`), isort (`I`).
+select = ["E", "F", "I"]
 ignore = []
 
 # Allow fix for all enabled rules (when `--fix`) is provided.