Travis fails on py3.6 only

See https://travis-ci.org/apertium/apertium-apy/builds/629740653

```
======================================================================

FAIL: test_analyze (tests.test.TestAnalyzeHandler)

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/virtualenv/python3.6.7/lib/python3.6/site-packages/tornado/testing.py", line 120, in __call__

result = self.orig_method(*args, **kwargs)

File "/home/travis/build/apertium/apertium-apy/tests/test.py", line 319, in test_analyze

self.assertEqual(response, [['ikkje/ikkje', 'ikkje']])

AssertionError: Lists differ: [] != [['ikkje/ikkje', 'ikkje']]

Second list contains 1 additional elements.

First extra element 0:

['ikkje/ikkje', 'ikkje']

- []

+ [['ikkje/ikkje', 'ikkje']]

======================================================================

FAIL: test_coverage (tests.test.TestCoverageHandler)

----------------------------------------------------------------------

[W 191226 18:44:43 apy:70] Caught signal: 15

Traceback (most recent call last):

File "/home/travis/virtualenv/python3.6.7/lib/python3.6/site-packages/tornado/testing.py", line 120, in __call__

result = self.orig_method(*args, **kwargs)

File "/home/travis/build/apertium/apertium-apy/tests/test.py", line 396, in test_coverage

self.assertListEqual(response, [0.5])

AssertionError: Lists differ: [1.0] != [0.5]

First differing element 0:

1.0

0.5

- [1.0]

+ [0.5]

======================================================================

FAIL: test_identify_lang (tests.test.TestIdentifyLangHandler)

----------------------------------------------------------------------

Traceback (most recent call last):

File "/home/travis/virtualenv/python3.6.7/lib/python3.6/site-packages/tornado/testing.py", line 120, in __call__

result = self.orig_method(*args, **kwargs)

File "/home/travis/build/apertium/apertium-apy/tests/test.py", line 390, in test_identify_lang

self.assertAlmostEqual(response['nno'], 1.0)

AssertionError: -1 != 1.0 within 7 places

----------------------------------------------------------------------

Ran 32 tests in 3.447s

FAILED (failures=3, skipped=1)
```

I don't understand why this just happens with 3.6