Captcha handling is not supported currently I guess. Maybe it was previously. Either (re-)enable captcha for not autoconfirmed users or show a more informative error message. (See https://www.mediawiki.org/wiki/Topic:Vrl03a6g6zrlpgps)
```
Traceback (most recent call last):
File "pwb.py", line 360, in <module>
if not main():
File "pwb.py", line 352, in main
run_python_file(filename,
File "pwb.py", line 73, in run_python_file
exec(compile(source, filename, 'exec', dont_inherit=True),
File "./scripts/login.py", line 185, in <module>
main()
File "./scripts/login.py", line 167, in main
site.login(autocreate=autocreate)
File "/home/yutkeej/pywikibot/pywikibot/tools/__init__.py", line 1499, in wrapper
return obj(*__args, **__kw)
File "/home/yutkeej/pywikibot/pywikibot/site/__init__.py", line 1931, in login
if login_manager.login(retry=True, autocreate=autocreate):
File "/home/yutkeej/pywikibot/pywikibot/login.py", line 301, in login
cookiedata = self.getCookie()
File "/home/yutkeej/pywikibot/pywikibot/tools/__init__.py", line 1584, in wrapper
return obj(*new_args, **new_kwargs)
File "/home/yutkeej/pywikibot/pywikibot/data/api.py", line 3197, in getCookie
and (response['messagecode'] == 'login-throttled'
KeyError: 'messagecode'
CRITICAL: Exiting due to uncaught exception <class 'KeyError'>
```