pyproject(ruff): Add flake8-errmsg

See also:
- https://docs.astral.sh/ruff/rules/#flake8-errmsg-em
- https://pypi.org/project/flake8-errmsg/

Author: tony

pyproject.toml

@@ -126,6 +126,7 @@ select = [
   "B", # flake8-bugbear
   "C4", # flake8-comprehensions
   "COM", # flake8-commas
+  "EM", # flake8-errmsg
   "Q", # flake8-quotes
   "PTH", # flake8-use-pathlib
   "SIM", # flake8-simplify