[issue7677] upload: improve display for error messages from gpg

[Éric Araujo]

Changes by Éric Araujo <merwok at netwok.org>:


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title: improve error message for setup.py upload --sign without --identity -> upload: improve display for error messages from gpg

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue7677>
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