[noetic] Fix install and improve Python 3 support

[mikaelarguedas]

This PR allow the capability server to start, currently it fails with:

/usr/bin/env: ‘python’: No such file or directory

The third commit runs modernize on the codebase which fixed all the Python3 problems I was facing when trying to run the demo

[mikaelarguedas]

Remaining test failures are due to the package pycodestyle having a faulty rosdep rule (ros/rosdistro#27546) and is unrelated to this change

[mikaelarguedas]

@ros-pull-request-builder retest this please

[stwirth]

👍

[mikaelarguedas]

@cottsay @sloretz how does that PR following your work of porting to python3 look to you?
Do you think we could get this merged and released in Noetic ?

[Rezenders]

Just pinging this thread. Is it possible to merge it?
I tested @mikaelarguedas modifications with python3 and it worked.

@wjwwood @cottsay @sloretz

[mikaelarguedas]

agreed, modernize tends to introduce unnecessary changes.
As there is interest in this PR, happy to take a stab at reducing the number of unnecessary changes added by it.
I do not have the setup I used it to test it last anymore though

[mikaelarguedas]

@wjwwood Here is a shorter version of this PR, PTAL.
I removed the list that seemed unnecessary, ended up adding back a couple in the places where elements from the dicts were being deleted within the loop.
Also took advantage to use YAML's Safe Loader to silence some warning.

@stwirth @Rezenders could you check if this version works for you ?

[wjwwood]

I'm not sure what the source of the error from travis-ci is, but it would be best to fix that.

The melodic failure looks related:

TypeError: unicode argument expected, got 'str'