From time to time test_pagegen_i18n_input fails because nothing was returned:
```
======================================================================
FAIL: test_pagegen_i18n_input (tests.i18n_tests.InputTestCase)
Test i18n.input via .
----------------------------------------------------------------------
Traceback (most recent call last):
File "/home/travis/build/wikimedia/pywikibot-core/tests/i18n_tests.py", line 357, in test_pagegen_i18n_input
self.assertIn('Please enter the category name:', result['stderr'])
AssertionError: u'Please enter the category name:' not found in u''
----------------------------------------------------------------------
```
* https://travis-ci.org/wikimedia/pywikibot-core/jobs/63187796#L2778
* https://travis-ci.org/wikimedia/pywikibot-core/jobs/59292510#L2686
* https://travis-ci.org/jayvdb/pywikibot-core/jobs/61779692#L3170
* https://travis-ci.org/jayvdb/pywikibot-core/jobs/61716096
* https://travis-ci.org/jayvdb/pywikibot-core/jobs/59381390
* https://travis-ci.org/jayvdb/pywikibot-core/jobs/57256079#L2679
* https://travis-ci.org/jayvdb/pywikibot-core/jobs/57565677#L2082