Travis CI build failing

[JoshGutman]

The last successful build was #737 on 10/23/18. Now, every build fails during the flake8 command:

The command "flake8 ." failed and exited with 1 during .

Taking a look at the output of the pip install command, we can see different versions for a few of the dependencies:

Success (10/23/18): Successfully installed chardet-3.0.4 consecution coverage-4.5.1 coveralls-1.5.1 docopt-0.6.2 flake8-3.5.0 graphviz-0.10idna-2.7 mccabe-0.6.1pycodestyle-2.3.1 pyflakes-1.6.0 requests-2.20.0 urllib3-1.24

Fail (10/24/18): Successfully installed chardet-3.0.4 consecution coverage-4.5.1 coveralls-1.5.1 docopt-0.6.2 flake8-3.6.0 graphviz-0.10.1idna-2.7 mccabe-0.6.1pycodestyle-2.4.0 pyflakes-2.0.0 requests-2.20.0 urllib3-1.24

The Travis CI docs suggest locking in the dependencies to the last working version, so maybe the solution would be to explicitly set the versions for the dependencies in setup.py here.

[robdmc]

I've been a bit awol the past few months. Thanks for raising issue. I'll address it soon.