fix: ziptheme.zip block removing test temporary directory on Windows.

tests/util.py

@@ -21,6 +21,7 @@ except ImportError:
     wraps = lambda f: (lambda w: w)
 
 from sphinx import application
+from sphinx.theming import Theme
 from sphinx.ext.autodoc import AutoDirective
 
 from path import path
@@ -170,6 +171,7 @@ class TestApp(application.Sphinx):
                                     freshenv, warningiserror, tags)
 
     def cleanup(self, doctrees=False):
+        Theme.themes.clear()
         AutoDirective._registry.clear()
         for tree in self.cleanup_trees:
             shutil.rmtree(tree, True)