[Python-Dev] Raising OSError concrete classes from errno code

[Serhiy Storchaka]

It sould be in Python-Ideas: add keyword argument support for OSError 
and subclasses with suitable default values. I.e.

 >>> OSError(errno=errno.ENOENT)
FileNotFoundError(2, 'No such file or directory')
 >>> FileNotFoundError(filename='qwerty')
FileNotFoundError(2, 'No such file or directory')
 >>> FileNotFoundError(strerr='Bad file')
FileNotFoundError(2, 'Bad file')