Spack-builder: spack-builder:ubuntu20.10 prints errors on load on rhel7 (cvmfswrite)

[wdconinc]

Steps to reproduce the issue

singularity run -B /cvmfs:/cvmfs docker://electronioncollider/spack-builder:ubuntu20.10 /bin/bash

Information on your system

$ singularity --version
2.6.1-dist

Additional information

Traceback (most recent call last):
  File "/spack/bin/spack", line 64, in <module>
    sys.exit(spack.main.main())
  File "/spack/lib/spack/spack/main.py", line 716, in main
    print_setup_info(*args.print_shell_vars.split(','))
  File "/spack/lib/spack/spack/main.py", line 669, in print_setup_info
    specs = spack.store.db.query(module_spec)
  File "/spack/lib/spack/llnl/util/lang.py", line 580, in __getattr__
    return getattr(self.ref_function(), name)
  File "/spack/lib/spack/spack/store.py", line 86, in <lambda>
    db = llnl.util.lang.LazyReference(lambda: store.db)
  File "/spack/lib/spack/llnl/util/lang.py", line 552, in __getattr__
    return getattr(self.instance, name)
  File "/spack/lib/spack/llnl/util/lang.py", line 548, in instance
    self._instance = self.factory()
  File "/spack/lib/spack/spack/store.py", line 78, in _store
    spack.config.get('config:install_hash_length'))
  File "/spack/lib/spack/spack/store.py", line 62, in __init__
    root, upstream_dbs=retrieve_upstream_dbs())
  File "/spack/lib/spack/spack/database.py", line 347, in __init__
    fs.mkdirp(self._db_dir)
  File "/spack/lib/spack/llnl/util/filesystem.py", line 582, in mkdirp
    raise e
OSError: [Errno 13] Permission denied: '/.spack-db'

Possible culprits: some environment variables are not inherited, tcsh is not playing nice with bash

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