plone.app.theming diazo when in Zope Control Panel

[yurj]

To reproduce:

1. go to Plone Control Panel -> Management Interface
2. Click on Control Panel (top right)
3. in the instance logs, you get:

2021-11-16 13:15:23,774 ERROR   [plone.transformchain:69][waitress-2] Unexpected error whilst trying to apply transform chain
Traceback (most recent call last):
  File "/home/yurj/.buildout/buildout-cache/eggs/plone.transformchain-2.0.2-py3.9.egg/plone/transformchain/transformer.py", line 59, in __call__
    newResult = handler.transformIterable(result, encoding)
  File "/home/yurj/.buildout/buildout-cache/eggs/plone.app.theming-5.0.0a3-py3.9.egg/plone/app/theming/transform.py", line 166, in transformIterable
    transform = self.setupTransform(runtrace=runtrace)
  File "/home/yurj/.buildout/buildout-cache/eggs/plone.app.theming-5.0.0a3-py3.9.egg/plone/app/theming/transform.py", line 92, in setupTransform
    transform = compileThemeTransform(
  File "/home/yurj/.buildout/buildout-cache/eggs/plone.app.theming-5.0.0a3-py3.9.egg/plone/app/theming/utils.py", line 716, in compileThemeTransform
    compiledTheme = compile_theme(
  File "/home/yurj/.buildout/buildout-cache/eggs/diazo-1.4.1-py3.9.egg/diazo/compiler.py", line 129, in compile_theme
    rules_doc = process_rules(
  File "/home/yurj/.buildout/buildout-cache/eggs/diazo-1.4.1-py3.9.egg/diazo/rules.py", line 293, in process_rules
    rules_doc = etree.parse(rules, parser=rules_parser)
  File "src/lxml/etree.pyx", line 3521, in lxml.etree.parse
  File "src/lxml/parser.pxi", line 1859, in lxml.etree._parseDocument
  File "src/lxml/parser.pxi", line 1885, in lxml.etree._parseDocumentFromURL
  File "src/lxml/parser.pxi", line 1789, in lxml.etree._parseDocFromFile
  File "src/lxml/parser.pxi", line 1177, in lxml.etree._BaseParser._parseDocFromFile
  File "src/lxml/parser.pxi", line 615, in lxml.etree._ParserContext._handleParseResultDoc
  File "src/lxml/parser.pxi", line 721, in lxml.etree._handleParseResult
  File "src/lxml/etree.pyx", line 318, in lxml.etree._ExceptionContext._raise_if_stored
  File "src/lxml/parser.pxi", line 448, in lxml.etree._local_resolver
  File "src/lxml/docloader.pxi", line 150, in lxml.etree._ResolverRegistry.resolve
  File "/home/yurj/.buildout/buildout-cache/eggs/plone.app.theming-5.0.0a3-py3.9.egg/plone/app/theming/utils.py", line 190, in resolve
    response = subrequest(system_url, root=root)
  File "/home/yurj/.buildout/buildout-cache/eggs/plone.subrequest-1.9.3-py3.9.egg/plone/subrequest/__init__.py", line 104, in subrequest
    root.virtual_url_path(),
AttributeError: 'RequestContainer' object has no attribute 'virtual_url_path'

shouldn't Diazo be inactive on Zope? Anyway, the error is only on zope Control_Panel.