message: clarified setup.py error message
diff: @@ -6,8 +6,11 @@ import sys, re, os
  try:
  from skbuild import setup
  + import pybind11
  except ImportError:
  - print("Please update pip: version 10 or greater is required.",
  + print("The preferred way to invoke 'setup.py' is via pip, as in 'pip "
  + "install .'. If you wish to run the setup script directly, you must "
  + "first install the build dependencies listed in pyproject.toml!",
  file=sys.stderr)
  raise
  