We do not have packaged furo and it is not needed to run tests.

--- zope.interface-7.1.1/setup.py.orig
+++ zope.interface-7.1.1/setup.py
@@ -142,7 +142,7 @@
     extras_require={
         'docs': ['Sphinx',
                  'repoze.sphinx.autointerface',
-                 'furo'],
+                 ],
         'test': tests_require,
         'testing': testing_extras,
     },