gh-76007: Deprecate __version__ attribute in imaplib

[hugovk]

Also remove it from the debug output:

         if __debug__:
             self._cmd_log_len = 10
             self._cmd_log_idx = 0
             self._cmd_log = {}           # Last '_cmd_log_len' interactions
             if self.debug >= 1:
-                self._mesg('imaplib version %s' % __version__)
                 self._mesg('new IMAP4 connection, tag=%s' % self.tagpre)

@picnixz Or would you prefer to put the Python version here?

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📚 Documentation preview 📚: https://cpython-previews--140299.org.readthedocs.build/

• Issue: Misleading __version__ attribute of modules in standard library #76007

[picnixz]

I think it is fine to remove it. We anyway have a divergence between 3.13 and 3.14 because 3.14 had a new feature and 3.13 and 3.14 had bugfixes that I addes, so it would only help if we had both the version of Python and the IMAP one.

IMO such debugging information could only be useful if the Python version also included the git commit it is based on but that would be an overkill I think.

[vstinner]

Suggested change

	return "2.50" # Do not change
	return "2.60" # Do not change