A once off error, could be a termporary or intermittent problem with archive.org
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FAIL: testInternetArchiveOlder (tests.weblinkchecker_tests.WeblibTestMementoInternetArchive)
Test Internet Archive for https://google.com as of June 2006.
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Traceback (most recent call last):
File "/home/travis/build/wikimedia/pywikibot-core/tests/weblib_tests.py", line 61, in testInternetArchiveOlder
self.assertIn('200606', parsed.path)
AssertionError: u'200606' not found in u'/web/20060531100101/http://www.google.com/'https://travis-ci.org/wikimedia/pywikibot-core/jobs/79710981#L3526