Issue 4373 - Made jshydra compatible with Python 3

tox.ini

+[tox]
+envlist = py27,py35
+skipsdist = true
+
+[testenv]
+commands = python autotest.py

[Sebastian Noack, 2016/08/28 22:36:14]

Note that in order to test all code paths, we'd have to make sure that there is
no cached mozilla* directory, then run utils.ensureJSShell(), and then make sure
it runs again. That would be easy enough here:

  commands =
    rm -rf mozilla*
    python -c 'import utils; utils.ensureJSShell()
    python autotest.py

But then we'd always have to download jsshell (once per environment!) on every
run. This would make the tests extremely slow, impossible to work offline, and
causing unnecessary load on Mozilla's servers.

Theoretically, we could bundle a version of the jsshell package with the tests
of course. However, the whole point of that code is to avoid bundling jsshell
with our code.

So I guess, I will just leave it as it is.

[Vasily Kuznetsov, 2016/08/29 15:29:52]

What you say makes sense, however, downloading uses slightly different code
paths in Python2/3 so perhaps it would be good to add (not included by default)
environments that would do the `rm -rf ...` and a comment about why they are
needed. This way this knowledge will not only be in this review.

[Sebastian Noack, 2016/08/30 11:44:38]

There you go, however, I decided to check for an optional argument, rather than
using separate environments. The main problem with using a separate environment
(besides being unnecessary) is that we want to test that code paths on all
Python versions. That would be possible with a factor condition, but you would
still have to explicitly specify all Python versions when running tox (i.e. "tox
-e py{27,35}-nocache").

[Vasily Kuznetsov, 2016/08/30 13:16:30]

Great, this is even better.