- python: only specify --install-{scripts,lib,data} if the   attributes/flags are set in fpm.
- python: only specify --install-{scripts,lib,data} if the
  attributes/flags are set in fpm.

  This should fix #273 without breaking prior behavior.

djhaskin987/fpm,djhaskin987/fpm,djhaskin987/fpm,djhaskin987/fpm