[TAAS-85] Upgrade to Python3

[lazysoundsystem]

https://humanitarian.atlassian.net/projects/TAAS/issues/TAAS-85

A couple of minor changes to prevent errors and to replace the codeclimate tests, detailed on the ticket.

This PR should test whether the Travis changes are okay.

[lazysoundsystem]

Travis did have some comments - including an objection to xenon:

0.08s$ xenon xenon -bB -mA -aA
No command 'xenon' found, did you mean:
 Command 'xeno' from package 'xenomai-runtime' (universe)
xenon: command not found
The command "xenon xenon -bB -mA -aA" exited with 127.

I'm not sure if this can be/ needs to be added back later.

[emmajane]

@lazysoundsystem it looks like Xenon measures code complexity: https://pypi.org/project/xenon/. This is arguably good to have but not necessarily required for the project to run...

[lazysoundsystem]

@emmajane - yes, I'm also guessing @cafuego will know what the issue is and we'll be able to re-instate it. (I presumed that having it in requirements.txt is enough for travis to load it and know it exists, but apparently not.)

Plus, I'd have to dive quite a bit deeper into Python to even consider making the code more complex!

[cafuego]

Hmm, the only xenon I know of is the noble gas :-)

[cafuego]

Ok, travis says:

ERROR: python-coveralls 2.9.0 has requirement coverage==4.0.3, but you'll have coverage 4.5.3 which is incompatible.
ERROR: xenon 0.5.5 has requirement PyYAML<5.0,>=4.2b1, but you'll have pyyaml 5.1.1 which is incompatible.

So I guess we won't be using it for a while.

[lazysoundsystem]

@cafuego - Looks like we're at an impasse with Xenon - looks like it can't be added back easily, but can we agree that it doesn't need to be added back at this stage?

[teodorescuserban]

It doesn't.