Describe the bug
pytest unit test fails in Docker container built from ludwig Dockerfile.

To Reproduce
Steps to reproduce the behavior:

1. Bild Ludwig Docker image: cd ludwig && docker build -t ludwig .
2. Run Ludwig docker container: docker run -it --rm --entrypoint /bin/bash ludwig
3. Within the container execute the following:

cd /ludwig
pytest  -v tests/integration_tests/test_api.py

Expected behavior
The tests should have passed, instead of failing

Screenshots
root@a69758374059:/ludwig# pytest -v tests/integration_tests/test_api.py
======================================================== test session starts =========================================================
platform linux -- Python 3.6.8, pytest-5.0.0, py-1.8.0, pluggy-0.12.0 -- /usr/bin/python3
cachedir: .pytest_cache
rootdir: /ludwig
collected 1 item

tests/integration_tests/test_api.py::test_api_intent_classification ERROR [100%]

=============================================================== ERRORS ===============================================================
__________________________________________ ERROR at setup of test_api_intent_classification __________________________________________
file /ludwig/tests/integration_tests/test_api.py, line 72
def test_api_intent_classification(csv_filename):
E fixture 'csv_filename' not found

  available fixtures: cache, capfd, capfdbinary, caplog, capsys, capsysbinary, doctest_namespace, monkeypatch, pytestconfig, record_property, record_testsuite_property, record_xml_attribute, recwarn, tmp_path, tmp_path_factory, tmpdir, tmpdir_factory
  use 'pytest --fixtures [testpath]' for help on them.

/ludwig/tests/integration_tests/test_api.py:72
========================================================== warnings summary ==========================================================
/usr/local/lib/python3.6/dist-packages/tensorflow/python/pywrap_tensorflow_internal.py:15
/usr/local/lib/python3.6/dist-packages/tensorflow/python/pywrap_tensorflow_internal.py:15: DeprecationWarning: the imp module is deprecated in favour of importlib; see the module's documentation for alternative uses
import imp

/usr/local/lib/python3.6/dist-packages/tensorflow/contrib/lite/python/init.py:26
/usr/local/lib/python3.6/dist-packages/tensorflow/contrib/lite/python/init.py:26: PendingDeprecationWarning: WARNING: TF Lite has moved from tf.contrib.lite to tf.lite. Please update your imports. This will be a breaking error in TensorFlow version 2.0.
_warnings.warn(WARNING, PendingDeprecationWarning)

-- Docs: https://docs.pytest.org/en/latest/warnings.html
================================================ 2 warnings, 1 error in 2.68 seconds =================================================
root@a69758374059:/ludwig# exit

Environment (please complete the following information):

• OS: MacOS 10.14.5, Docker Desktop forMac 2.0.0.3
• Version
• Python version: 3.6.8 (from ludwig Dockerfile)
• Ludwig version: 0.1.2

*Additional context
I noticed PR #403 Commit 3533a4b removed the imports for the required pytest fixtures from tests/integration_tests/test_api.py, e.g.,

from tests.fixtures.filenames import csv_filename

Is there a different way to run the pytest tests? If desired, I can submit a PR to add the missing imports. I just need some guidance.