wraps behaves differently on 2.7 and 3.5

[benjaminp]

Originally reported by: Hexchain Tong (Bitbucket: hexchain, GitHub: hexchain)

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In Python 2.7 the wraps cannot be used on @classmethods because it does not have the __module__ attribute.

In Python 3.5 it has a try/except around setattr so nonexistent attributes are ignored silently.

Should six.wraps behave consistently across these versions? Thanks.

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• Bitbucket: https://bitbucket.org/gutworth/six/issue/165