zope.sendmail unnecessarily errors out when checking async directories

[Elizabeth Leddy]

Noticed when testing plone 4 beta 5, which uses zope 2.12.7, which looks to be zope.sendmail 3.5.1. Reviewing the changeset it doesn't look like this bug has been addressed but if so I apologize for double reporting.

For async queuing, if you select a default directory that already exists, i.e. /tmp (which is the default), and try to save the changes in the ZMI, the following error throws:

Traceback (innermost last):
  Module ZPublisher.Publish, line 127, in publish
  Module ZPublisher.mapply, line 77, in mapply
  Module ZPublisher.Publish, line 47, in call_object
  Module Products.MailHost.MailHost, line 187, in manage_makeChanges
  Module Products.MailHost.decorator, line 26, in method
  Module Products.MailHost.MailHost, line 298, in _startQueueProcessorThread
  Module zope.sendmail.delivery, line 229, in setQueuePath
  Module zope.sendmail.maildir, line 59, in __init__
ValueError: /tmp is not a Maildir folder

Digging in maildir.py, this looks like a simple fix on logic - if the base directory already exists it doesn't create the required subfolders, however it errors on the check for them:
    def __init__(self, path, create=False):
        ...
        if create and not access(path):
            os.mkdir(path)
            os.mkdir(subdir_cur)
            os.mkdir(subdir_new)
            os.mkdir(subdir_tmp)
            maildir = True
        else:
            maildir = (os.path.isdir(subdir_cur) and os.path.isdir(subdir_new)
                       and os.path.isdir(subdir_tmp))
        if not maildir:
            raise ValueError('%s is not a Maildir folder' % path)
       ....

On a somewhat related note, the names of those subfolders are extra generic and there is a potential that if people were to put that in /tmp as suggested, they would either get clobbered or accidentally deleted. This could be easily fixed with the fix + a better default.

[Colin Watson (cjwatson)]

The zope.sendmail project on Launchpad has been archived at the request of the Zope developers (see https://answers.launchpad.net/launchpad/+question/683589 and https://answers.launchpad.net/launchpad/+question/685285). If this bug is still relevant, please refile it at https://github.com/zopefoundation/zope.sendmail.

[Colin Watson (cjwatson)]

The zope2 project on Launchpad has been archived at the request of the Zope developers (see https://answers.launchpad.net/launchpad/+question/683589 and https://answers.launchpad.net/launchpad/+question/685285). If this bug is still relevant, please refile it at https://github.com/zopefoundation/zope2.