Failing CI feature tests caused by docker warning message about the kernel

[michaelbarton]

The current commit 3b13fc6 on the release/0.3.0 branch is failing on
the CI server. After some investigation I have found what is causing
the error. I'll write up the details here as this might help with similar
problems when debugging the verification functionality of the command line
interface.

• The verification part of the CLI runs cucumber feature files which are
  maintained in the biobox_cli/verification folder. Each feature file file
  specifies how a how biobox type should behave - for example a feature file
  for a short read assembler, which tests out different user inputs - both
  correct and incorrect.
• These verification feature files are part of the UX and so must be tested to
  ensure they do not break between builds. Therefore these feature files have
  corresponding feature files in the feature directory. This essentially is
  testing the testing code.
• In commit 3b13fc6 the cucumber features for verification fail for
  the short read assembler biobox on the CI server but work when run locally.
  This indicates a problem specifically for the CI server environment.
• I logged into circleci using the ssh button. This reruns the same failing
  build and also allows ssh access during the build. This makes interactive
  debugging possible as I can log in, rerun the feature tests, and inspect
  the outputs.
• Each time a feature test is run, any created files are stored in the
  temporary directory tmp under the project root. The verification test
  output files are however not stored in this folder because they are being
  run indirectly by the top level feature tests. Instead the tmp folder
  contains the JSON output for each verification test.
• This JSON contains the reason why a verification test fails. The
  verification code in the CLI parses this file for the failing scenario
  message. If there is an unsual reason why a verification test failed, this
  JSON file will contain the output. Specifically in the instance of this bug
  the error message is being written on the stderr when the feature test
  expects none to be produced:

"error_message": [
"Assertion Failed: The stderr should be empty but contains:",
"",
"WARNING: Your kernel does not support memory swappiness capabilities, memory swappiness discarded."
],
"status": "failed"

I contacted Circle CI and they say the LXC environment is responsible for this
error message.

[michaelbarton]

Fixed in #60