Add OSX on 3.6 and 3.7 to travis, use addons.apt:packages for graphviz

[bollwyvl]

This adds 3.6/3.7 OSX builds to the travis-ci matrix. No doubt this comes at greater cost to shared resources per PR, but so it goes!

In reading the Travis docs, this also moves the apt install up to the addon level, since we weren't pinning or anything. The equivalent brew command is also moved up to before_install. (not building docs on osx)

c/f conda-forge/ipython-feedstock#63 (comment)

[bollwyvl]

New matrix looks like I didn't screw anything major up... yet:

[bollwyvl]

Har:

3.6 is not installed; attempting download
Downloading archive: https://s3.amazonaws.com/travis-python-archives/binaries/osx/10.13/x86_64/python-3.6.tar.bz2
$ curl -sSf -o python-3.6.tar.bz2 ${archive_url}
curl: (22) The requested URL returned error: 403 Forbidden
Unable to download 3.6 archive. The archive may not exist. Please consider a different version.

[bollwyvl]

Right, about those docs... will brew up some python...

[bollwyvl]

Great, looks like the OSX CI is going through. The allowed nightly fail appears to not be related to this.

The first working 3.6 build took 8 minutes, and was slower to start anyway. Investigating whether caching the built pythons makes a net difference (of course, would need to succeed....)

[bollwyvl]

Oh, I love you, first ✔️. Ooh, and coverage went up!

[bollwyvl]

Ugh, looks like the cache situation isn't great: appears to have cached bin/ipython and friends, and we have no interest in that. So, we're looking at 8-9 minutes for the OSX builds at present. Thoughts?

[minrk]

Updating homebrew and building Python from source with pyenv both take a pretty long time. I added a commit with a couple small changes:

• only install Python if not present
• install Python binaries from Python.org instead of from source
• avoid updating homebrew

The mac builds now complete in 3 minutes.

[bollwyvl]

Fantastic. I don't have a Mac so was stumbling in the dark a bit. Also +1 to yaml formatting... api_key might still be indented too far. Moving to a virtualenv may have missed a few test cases, but I can't interpret the codecov results properly on my phone!

[Carreau]

Do we still have a JS group ?

+1 will look at it closer from my phone.

[Carreau]

*from my desktop

[bollwyvl]

Do we still have a JS group ?

No, removed!

[bollwyvl]

Here's the only virtualenv coverage change:

https://codecov.io/gh/ipython/ipython/compare/70d51e3...a39b70da8c26968e72342f231f9349cc52fd69b5/changes

Probably not worth worrying about.

[bollwyvl]

Hooray!