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Describe the bug

root-config --has-XXX simply prints "no" and returns 0 if XXX is not a ROOT feature. This is an unnecessary source of confusion (see e.g. this forum thread), especially when features change name, as it happened with --has-python which is now spelled --has-pyroot, or in case of spelling mistakes root-config --has-builtin-cling prints "no" but root-config --has-builtin_cling prints "yes".

Expected behavior

root-config --has-bugs should print something like "unknown feature: 'bugs'" and root-config should return non-zero.