BigQuery: ability to set default job / table / dataset configs in client class

[tswast]

The location is considered a global parameter (by the the BigQuery engineering team and the bq command-line tool), and we are tracking the feature to set a default location at #5148.
There are other non-global properties where it would be useful to set a user-configurable default.

For example:

• Labels on jobs. It could be useful to set default labels so that folks can track more easily which jobs are getting run by which application.
• use_legacy_sql on QueryJobConfig. Right now this defaults to standard SQL syntax, but some people might prefer to use legacy SQL for existing queries.
• The destination_encryption_configuration in jobs and the encryption_configuration in tables. Maybe this one actually makes sense as a global parameter, but it's not considered on in the bq command-line tool.

[blainehansen]

I'm trying to put together a pull request for this, to get us to the behavior we're looking for that was mentioned in #6042 .

However, when trying to run nox, I'm getting errors that I wouldn't expect. For example:

$ nox -f bigquery/nox.py -s "unit(py='3.6')"
nox > Running session unit(py='3.6')
nox > Creating virtualenv using python3 in /home/blaine/experiments/google-cloud-python/.nox/unit-py-3-6
nox > Session unit(py='3.6') raised exception AttributeError("'Session' object has no attribute 'interpreter'",)
Traceback (most recent call last):
  File "/home/blaine/.local/lib/python3.6/site-packages/nox/sessions.py", line 297, in execute
    self.func(session)
  File "/home/blaine/.local/lib/python3.6/site-packages/nox/_parametrize.py", line 92, in call_wrapper
    return func(*args, **kwargs)
  File "/home/blaine/experiments/google-cloud-python/bigquery/nox.py", line 76, in unit
    session.interpreter = 'python{}'.format(py)
AttributeError: 'Session' object has no attribute 'interpreter'
nox > Session unit(py='3.6') failed.

This makes sense, since it seems nox sessions don't have an interpreter attribute (nor a virtualenv_dirname for that matter, which is also set in that method). But it's surprising to me that these errors are popping up for me? Am I running in a context I shouldn't be? Why is the nox file setting non-existent attributes?

[tseaver]

@blainehansen I was just able to run the tests using the command line you provided. Note that we would normally run from inside the bigquery directory). Do you have python3.6 on your $PATH when you start?

[tswast]

I think the Nox error may be due to nox (new incompatible package) versus nox-automation package (what google-cloud-python still uses AFAIK)

[blainehansen]

⬆️ This sounds right. The error I'm getting is a basic python problem (can't assign to a non-existent attribute) so it suggests a misalignment between the code I'm running in the project and the version of nox I have.

I don't know if this is helpful but:

$ nox --version
2018.9.14

Also:

$ which python3.6
/usr/bin/python3.6
$ echo $PATH
...redacted
:/usr/bin:
...redacted

[blainehansen]

Yep, installing and using nox-automation fixed it :) 🎊 🎊