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I found errno.EROFS in Lib/mailbox.py but didn't find exception correspond to this errno. Is it need to be created?

Also:
errno.EXDEV in Lib/distutils/file_util.py
errno.ENOTCONN in Lib/poplib.py
errno.EINVAL in Lib/subprocess.py
errno.ENOTCONN in Lib/smtpd.py, Lib/ssl.py, Lib/imaplib.py
errno.EOPNOTSUPP, errno.ENOTSUP, errno.ENOTSUP, errno.ENODATA in Lib/shutil.py 

The rationale for not creating dedicated exception classes is that those errors are not common enough. Since the range of possible errno values is basically unbounded (each system can create their own system-specific errors), trying to cover them all is a losing battle.

Sorry for reopening.
Do you really sure that ENOTCONN and EINVAL doesn't worth to have separate sublasses?
The same question about Not Supported family.
I don't force to make new exception classes, just like to figure out the status quo.
If we decide to keep in stone our exceptions hierarchy for OSError's — that's ok.
If list is open — let's discuss

Antoine will have to decide on this, but IMO now that we released the PEP 3151 set in Python 3.3, we should not continue adding new builtin exceptions in every release.

A bit in detail:
- ENOTCONN is a programming error, so there's no use actually catching it (you should fix the bug instead when you encounter it)
- EINVAL could be a candidate, but unfortunately it would clash quite nastily with ValueError and lead to confusion; therefore I think it's better not wrapping it

Ok. Antoine's comment is clean.
Let's close the issue.