An example
ERROR: test_fully_qualified_NS1_family (tests.link_tests.TestFullyQualifiedNoLangFamilyExplicitLinkParser)
Test ':wikidata:testwiki:Talk:Q6' on enwp is namespace 1.
Traceback (most recent call last):
File "/home/travis/build/wikimedia/pywikibot-core/tests/link_tests.py", line 372, in test_fully_qualified_NS1_family link.parse() File "/home/travis/build/wikimedia/pywikibot-core/pywikibot/page.py", line 4154, in parse if hasattr(self._site.namespaces()[self._namespace], 'case'):
KeyError: 0
Many more here:
https://travis-ci.org/wikimedia/pywikibot-core/jobs/39676782
And I'm quite confident there was another build in the last few weeks which has done this.
Version: core-(2.0)
Severity: normal