message: Automatically add pybind11 to setup.py cmake args
  This checks if pybind11 was installed via pip. If it was,
  then it will automatically include the pybind11 directory in
  the cmake arguments.
diff: @@ -20,6 +20,14 @@ cmake_args = [
  '-DUSE_LIBMSYM:BOOL=FALSE',
  ] + extra_cmake_args()
  +# Add pybind11 if it is installed
  +try:
  + from pybind11 import get_cmake_dir
  +except ImportError:
  + pass
  +else:
  + cmake_args.append('-Dpybind11_DIR:PATH=' + get_cmake_dir())
  +
  setup(
  name='avogadro',
  use_scm_version=True,
  