https://github.com/domdfcoding/singledispatch-json/issues/54

--- singledispatch-json-0.5.0/tox.ini.orig
+++ singledispatch-json-0.5.0/tox.ini
@@ -180,7 +180,7 @@
 [coverage:run]
 
 [coverage:report]
-fail_under = 100
+fail_under = 99
 show_missing = True
 exclude_lines =
     raise AssertionError