Add Python 3.5 system-test target in tox.ini

[duggelz]

Currently it has 'system-test' -> python 2.7 and 'system-test3' -> python 3.4

See also #2350

[dhermes]

@duggelz Thanks for taking an interest in our test setup. Any particular reason this matters to you? Keep in mind you can already run the system tests in Python 3.5 if you please via:

$ git clone https://github.com/GoogleCloudPlatform/google-cloud-python
$ cd google-cloud-python/
$ virtualenv --python=python3.5 venv
$ source venv/bin/activate
(venv) $ venv/bin/pip install core/
(venv) $ venv/bin/pip install \
> bigtable/ \
> storage/ \
> datastore/ \
> bigquery/ \
> pubsub/ \
> logging/ \
> dns/ \
> language/ \
> error_reporting/ \
> resource_manager/ \
> monitoring/ \
> vision/ \
> translate/ \
> speech/
(venv) $ venv/bin/python system_tests/attempt_system_tests.py
(venv) $ deactivate
$ rm -fr venv/

[duggelz]

I can run the tests as you describe, but a tox target is much nicer, since I already use tox to run the tests against Python 2.7 and 3.4

[dhermes]

Anything wrong with just making system-tests3 use py3.5 instead of py3.4?

[duggelz]

Sure, I can do that. But your documentation specifically calls out 2.7, 3.4, and 3.5 as the supported versions, so it seems like you'd want to test on all those versions.

- The feature must work fully on the following CPython versions:  2.7,
  3.4, and 3.5 on both UNIX and Windows.

[tseaver]

Sure, I can do that. But your documentation specifically calls out 2.7, 3.4, and 3.5 as the supported versions, so it seems like you'd want to test on all those versions.

Our unit test coverage is really good: it is super unlikely that running system tests on 3.4 and 3.5 will show any 3.5-only breakage not already caught by the unit tests (which we do run on both). The difference is that system tests take minutes to run, rather than seconds.

[duggelz]

Done. Please take a look #2741

[duggelz]

This issue is closed, right? Do I need to do something more?