Cannot use special chars in package names in LHCBEXTERNALS_##.json

For example, with herwig++ in the list of packages we get:

$ lb-create-all-lcg-meta-specs 'LCG_{lcg_version}LHCb_{platform}' LCG_97a_platforms.txt LHCBEXTERNALS_97a_LHCB_2.json 
WARNING:root:Loading list of externals from file
WARNING:lbinstall.db.DBManager:Creating new local package DB at /tmp/siteroot/var/lib/db/packages.db
Traceback (most recent call last):
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/bin/lb-create-all-lcg-meta-specs", line 8, in <module>
    sys.exit(main())
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/site-packages/LbAdmin/CreateAllSpecs.py", line 69, in main
    f = createSpec(p, args.external_list_json, output , release=args.release,
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/site-packages/LbAdmin/CreateLHCbLCGMetaSpec.py", line 281, in createSpec
    (lcgVer, requiresList) = getRequiresList(platform, filename)
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/site-packages/LbAdmin/CreateLHCbLCGMetaSpec.py", line 115, in getRequiresList
    res = vf.find(package)
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/site-packages/LbAdmin/CreateLHCbLCGMetaSpec.py", line 90, in find
    if re.match(extName, p):
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/re.py", line 191, in match
    return _compile(pattern, flags).match(string)
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/re.py", line 304, in _compile
    p = sre_compile.compile(pattern, flags)
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/sre_compile.py", line 764, in compile
    p = sre_parse.parse(p, flags)
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/sre_parse.py", line 948, in parse
    p = _parse_sub(source, state, flags & SRE_FLAG_VERBOSE, 0)
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/sre_parse.py", line 443, in _parse_sub
    itemsappend(_parse(source, state, verbose, nested + 1,
  File "/cvmfs/lhcb.cern.ch/lib/var/lib/LbEnv/936/unstable/linux-64/lib/python3.8/sre_parse.py", line 671, in _parse
    raise source.error("multiple repeat",
re.error: multiple repeat at position 23