director, drake_visualizer: Support Python 3

[EricCousineau-TRI]

Towards #10606

[EricCousineau-TRI]

@patmarion If you have a chance, can I ask if you have a release / non-volatile branch (one that won't get rebased / deleted after merge at least for a while) for Director Python 3?

You had mentioned the following one, but it's unclear what it's lifetime will be:
RobotLocomotion/director#625

UPDATE: Per discussion in the above director PR, Pat will be able to merge this to master.

[EricCousineau-TRI]

@jamiesnape Can I ask how things are going on this front? Is this something that we could start trying out (e.g. in Anzu) before we remove Mac + Python 2 support? (to at least make sure there're no "platform independent" errors)

(Or should we separate out the removal of Mac Python 2 support?)

[jamiesnape]

Should be ready tomorrow. Everything builds fine, just have not checked if it actually runs.

[EricCousineau-TRI]

A user ran into the issue captured in #11134:
https://stackoverflow.com/questions/58270730/drake-frame-visualization-attribute-error
This will be resolved by updating Director, at least on modern platforms (Bionic).

Can I ask when we might have this on Drake master?

[jamiesnape]

It's in the queue for Mac, for Bionic after that, so probably late this week.

[felixcrazzolara]

I'm looking forward to it :)

[EricCousineau-TRI]

Per f2f, now aiming for 10/25 given other complications (Mac, Bazel, etc. shennanigans)

[jwnimmer-tri]

Sometime next week (or soon after) is our nominal 0.12.0 release tag. Be in touch with me if you'd like to ensure that this fix specifically does or does not make it into the release.

[jamiesnape]

It probably should be in, but I would not say it should be a blocker. That said, the work is pretty much done, but if release can be the later part of the week, it gives more time to review and test (there is a lot of churn with Mac Python 3 versions at the moment, for instance).

[jamiesnape]

Draft PR is now up (#12296).