APISite.exturlusage() parameters are always None for defautl or False in case of content. But calling the method with default parameter fails with TypeError:
>>> import pywikibot as py
>>> s = py.Site()
>>> r = s.exturlusage()
Traceback (most recent call last):
File "<pyshell#6>", line 1, in <module>
r = s.exturlusage()
File "C:\pwb\GIT\core\pywikibot\tools\__init__.py", line 1449, in wrapper
return obj(*__args, **__kw)
File "C:\pwb\GIT\core\pywikibot\site\__init__.py", line 3909, in exturlusage
if separator in url:
TypeError: argument of type 'NoneType' is not iterable