$ spack -sd setup omega-h@local

...
lib/spack/spack/cmd/setup.py:178 ==> Generating spconfig.py [omega-h@local%clang@9.0.0-apple~bounds build_type= ~examples~mpi+optimize+shared+symbols~throw+trilinos+warnings~zlib arch=darwin-sierra-x86_64 /wfri2bq]
lib/spack/llnl/util/lock.py:353 ==> WRITE LOCK: /Users/daibane/src/spack/opt/spack/.spack-db/lock[0:0] [Released]
Traceback (most recent call last):
  File "/Users/daibane/src/spack/bin/spack", line 54, in <module>
    sys.exit(spack.main.main())
  File "/Users/daibane/src/spack/lib/spack/spack/main.py", line 653, in main
    return _invoke_command(command, parser, args, unknown)
  File "/Users/daibane/src/spack/lib/spack/spack/main.py", line 432, in _invoke_command
    return_val = command(parser, args)
  File "/Users/daibane/src/spack/lib/spack/spack/cmd/setup.py", line 181, in setup
    write_spconfig(package, dirty)
  File "/Users/daibane/src/spack/lib/spack/spack/cmd/setup.py", line 87, in write_spconfig
    env['FC'] = os.environ['SPACK_FC']
  File "/System/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/UserDict.py", line 23, in __getitem__
    raise KeyError(key)
KeyError: 'SPACK_FC'