StaticFile.__str__ should always return a str, not e.g. a Path() instance

Refs django-commons#2002

Author: matthiask

debug_toolbar/panels/staticfiles.py

@@ -21,7 +21,7 @@ def __init__(self, path):
         self.path = path
 
     def __str__(self):
-        return self.path
+        return str(self.path)
 
     def real_path(self):
         return finders.find(self.path)