[docs] [issue16785] Document the fact that constructing OSError with erron returns subclass if possible

Serhiy Storchaka added the comment: However

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OSError(errno.ENOENT) OSError(2,) OSError(errno.ENOENT, 'error msg', 'filename', 'spam') OSError(2, 'error msg', 'filename', 'spam')

---------- nosy: +serhiy.storchaka stage: -> needs patch type: -> enhancement _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue16785> _______________________________________