- remove the old LGPL license headers from all files in Spack
- add SPDX headers to all files
- core and most packages are (Apache-2.0 OR MIT)
- a very small number of remaining packages are LGPL-2.1-only
- py-setuptools is required by py-yt for importing yt in jupyter notebooks.
- add two dependencies needed for python 2.7
- add the py-subprocess32 package