Pin virtualenv pip package to pin installed binary

[aneeshusa]

I noticed homu broke (sometime today I guess) while working on another PR.

A recent update of the virtualenv package changed the installed
binaries from virtualenv and virtualenv-3.4, to virtualenv and
virtualenv-3.5, breaking the homu installation which needs a python3
version of virtualenv. Pin the package to the newest version and update
the homu installation to use the virtualenv-3.5 binary.

Note: the python3 apt package still installs python3.4, but the version
difference should be ok since virtualenv is just used to install homu,
not run it.

@Manishearth as I said in the commit message I don't think combining
python3.4 and virtualenv-3.5 should cause problems, but how can I test
homu manually to make sure it runs properly?

[Manishearth]

Pop some dummy values into the config (stick a valid github login and repo URL in it), and ensure service start homu outputs the following:

Bottle v0.12.9 server starting up (using WaitressServer())...
Listening on http://:54856/
Hit Ctrl-C to quit.

serving on http://0.0.0.0:54856

in /var/log/upstart/homu.log

[Manishearth]

This is what's currently on the server, btw:

root@servo-master:~# pip show virtualenv
---
Metadata-Version: 2.0
Name: virtualenv
Version: 1.11.6
Summary: Virtual Python Environment builder
Home-page: https://virtualenv.pypa.io/
Author: Jannis Leidel, Carl Meyer and Brian Rosner
Author-email: python-virtualenv@groups.google.com
License: MIT
Location: /usr/local/lib/python2.7/dist-packages
Requires: 
You are using pip version 7.1.2, however version 8.0.2 is available.
You should consider upgrading via the 'pip install --upgrade pip' command.
root@servo-master:~# pip3 show virtualenv
---
Name: virtualenv
Version: 13.1.2
Location: /usr/local/lib/python3.4/dist-packages
Requires: 

[aneeshusa]

OK, tested it locally and homu ran successfully. (It only needed an access token with the user:email scope.)

[Manishearth]

@bors-servo r+

Oh, yeah, that thing shouldn't actually be necessary (we don't use that setting); I should make it optional.

[bors-servo]

📌 Commit 2fe74b3 has been approved by Manishearth

[bors-servo]

⌛ Testing commit 2fe74b3 with merge 96fb503...

[aneeshusa]

I checked the homu source, and it looks like it wants access to the user:email data in order to have an email to use when making commits via git. For example, bors-servo commits with the email 'lbergstrom+bors@mozilla.com'. I guess this could be configured as a separate config option, but I do think it's useful to have an email associated with homu.

[Manishearth]

Oh ah. I was thinking about a different optional key which seems to now actually be optional.

[bors-servo]

☀️ Test successful - travis

[Manishearth]

Deployed, works. There's a virtualenv-3.4 still hanging around, but it's not breaking anything as far as I can tell.

[aneeshusa]

That's weird, I'm going to look into it. I don't want it causing any problems in the future (like #203).

[Manishearth]

That's probably because the salt-redeploy doesn't uninstall things?

[aneeshusa]

Well, the virtualenv pip package was already installed, so it should just update it to a newer version via pip. I'm guessing this is a pip behavior, but it could be due to Salt or the virtualenv package itself.