fixes for gpg.py extension
- add copyright and license
- add i18n
- add 'sigs' command behaving like 'hg tags'
- change 'role' to 'comment' and output it only if there is one
- refactoring
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abort: impossible time zone offset: 4444444
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abort: invalid date: '1\t15.1'
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abort: invalid date: 'foo bar'
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abort: invalid date: ' 1 4444'
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abort: date exceeds 32 bits: 111111111111
abort: No such file or directory: .../test/bar