Python 2 / 3 compatible imports.

[rudaporto]

@pbauer can you help me with this review or should I ask someone else?

[rudaporto]

@tomgross I update with more compatible changes.

• remove some unused imports of urllib.quote_plus
• change to use built-in set class when sets (deprecated) module is not available
• add six.text_type instead of unicode

Still, there is some unused imports but I did not removed them at this stage.

[rudaporto]

@tomgross should I change travis.yaml to use tox run the build with python 2.7, 3.4, 3.5 and 3.6?

[tomgross]

@rudaporto This package depends on GenericSetup (Python 3 upgrade is WIP) and ZServer (This package will probably never see Python 3)

To get an overview what is achieved it is probably a good idea to have them with allow_failures option on. I don't know, if there is an official statement on Python 3 subversion compatibility but I'd focus on 3.5 and 3.6.

[tomgross]

Maybe it is a good idea to have coveralls run too to see where the blind spots are.

[tomgross]

Apart from that this LGTM.

[tseaver]

We should make the dependency on ZServer optional. The dependency is there to support detection of an FTPRequest, but if ZServer is not installed, we can just create a no-op class, e.g.:

# in Products/PluggableAuthService/plugins/RequestTypeSniffer.py
try:
    from ZServer.FTPRequest import FTPReques
except ImportError:
    class FTPRequest(object):
        """Dummy for missing ZServer's 'FTPRequest'."""

[icemac]

@tseaver +1 to make ZServer optional, some weeks ago I created #8 to address this issue. Maybe it can be done in another PR.

[icemac]

What has still to be done to get this PR merged?