Steps to reproduce the issue

packages.yaml

packages:
  python:
    externals:
    - spec: 'python@3.8'
      # configure for module/path to system python paths not writable by user
    buildable: false

Install sz+python with spack

spack install sz+python

Error paraphrased

Cannot install sz python to <path/to/system/python/modules>, no write permissions

Information on your system

ORNL Spock

• Spack: 0.16.2-4028-d27e0bff5a
• Python: 3.6.13
• Platform: cray-sles15-zen2
• Concretizer: clingo

Additional information

maintainers: @disheng222 @robertu94

spack-build-env.txt
spack-build-out.txt

General information

• I have run spack debug report and reported the version of Spack/Python/Platform
• I have run spack maintainers <name-of-the-package> and @mentioned any maintainers
• I have uploaded the build log and environment files
• I have searched the issues of this repo and believe this is not a duplicate