Make finalizeSchema more robust by not handling behavior schema classes.

[mauritsvanrees]

This is for the branch used in Plone 5.2.
Backported from version 2.0, specifically PR #27 which was needed to get the dexterity site root working. I already commented there two years ago that I wondered if this would be safe for 5.2 as well.

This fixes test failures on Plone 5.2 Python 3 when used together with plone/plone.dexterity#189, which is a backport of a memory leak fix. Failures are like this:

File "/home/jenkins/.buildout/eggs/cp38/plone.autoform-1.9.1-py3.8.egg/plone/autoform/tests/../autoform.rst", line 50, in autoform.rst
Failed example:
    xmlconfig.xmlconfig(StringIO(configuration))
Exception raised:
    Traceback (most recent call last):
      File "/srv/python3.8/lib/python3.8/doctest.py", line 1336, in __run
        exec(compile(example.source, filename, "single",
      File "<doctest autoform.rst[11]>", line 1, in <module>
        xmlconfig.xmlconfig(StringIO(configuration))
      File "/home/jenkins/.buildout/eggs/cp38/zope.configuration-4.4.1-py3.8.egg/zope/configuration/xmlconfig.py", line 732, in xmlconfig
        context.execute_actions(testing=testing)
      File "/home/jenkins/.buildout/eggs/cp38/zope.configuration-4.4.1-py3.8.egg/zope/configuration/config.py", line 799, in execute_actions
        reraise(
      File "/home/jenkins/.buildout/eggs/cp38/zope.configuration-4.4.1-py3.8.egg/zope/configuration/_compat.py", line 31, in reraise
        raise value.with_traceback(tb)
      File "/home/jenkins/.buildout/eggs/cp38/zope.configuration-4.4.1-py3.8.egg/zope/configuration/config.py", line 791, in execute_actions
        callable(*args, **kw)
      File "/home/jenkins/.buildout/eggs/cp38/plone.supermodel-1.6.5-py3.8.egg/plone/supermodel/model.py", line 116, in finalizeSchemas
        for schema in sorted(schemas):
    zope.configuration.config.ConfigurationExecutionError: File "/home/jenkins/.buildout/eggs/cp38/plone.supermodel-1.6.5-py3.8.egg/plone/supermodel/configure.zcml", line 9.4-12.10
          <zcml:customAction
              handler=".model.finalizeSchemas"
              order="9999999"
              />

        TypeError: '<' not supported between instances of 'Provides' and 'InterfaceClass'

The test failures are mostly in plone.autoform and in plone.app.registry, but strangely you do not get the error when you run only the tests for one of those packages. You really need to run the entire Plone test suite (bin/test in coredev, without options). So there is likely some test leakage. See all failures on Jenkins.

Python 2 does not have this problem: sorting on Python 3 is handled differently. On Python 2:

>>> from zope.interface.declarations import Implements, Provides
>>> sorted([Implements(), Provides(object)])
[classImplements(?), directlyProvides(object)]

On Python 3:

>>> from zope.interface.declarations import Implements, Provides
>>> sorted([Implements(), Provides(object)])
Traceback (most recent call last):
  File "<console>", line 1, in <module>
TypeError: '<' not supported between instances of 'Provides' and 'Implements'

[mauritsvanrees]

I am testing this on Jenkins together with plone/plone.dexterity#189.

[gforcada]

LGTM! 💯

[mamico]

LGTM