Add defusedxml as test requirement

Until Sphinx v7.3.8 or v7.4.0 is released with [1] included.

[1] sphinx-doc/sphinx#12362

Signed-off-by: Stephen Finucane <stephen@that.guru>

Author: stephenfin

tox.ini

@@ -11,6 +11,7 @@ deps =
     pytest
     pytest-cov
     coverage
+    defusedxml
     click7: click>=7.0,<8.0
     click8: click>=8.0,<9.0
     click8-async: asyncclick>=8.0,<9.0