Adding check that all public modules are documented.

[dhermes]

Fixes#714.

Also: making prints to stderr Python 3 friendly in run_pylint.py.

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@tseaver Note the docs rule will fail here. This was intentional. I wanted to display which modules were still undocumented so we could discuss if they should be added to the IGNORED_MODULES set or if we should add them to an rst file.

[dhermes]

@tseaver PTAL

[dhermes]

@tseaver PTAL. This time docs should fail with an explanation of which modules we leave out.

At this point we should discuss which need to be actually documented and which I should add to IGNORE_MODULES.

When running locally, the errors are:

Found undocumented public modules:
- gcloud.bigquery.query
- gcloud.datastore.helpers
- gcloud.environment_vars
- gcloud.iterator
- gcloud.storage.batch
- gcloud.streaming.buffered_stream
- gcloud.streaming.exceptions
- gcloud.streaming.http_wrapper
- gcloud.streaming.stream_slice
- gcloud.streaming.transfer
- gcloud.streaming.util

[dhermes]

@tseaver PTAL

[tseaver]

LGTM

[dhermes]

@tseaver There are still questions to resolve.

We have several undocumented modules and need to decide which ones to ignore and which ones need documenting.

I expected the CI to fail but tox -e docs only gets run on merged commits or tagged commits (not on PRs).

[dhermes]

@tseaver PTAL, pending question above

[theacodes]

I think we should ignore:

• gcloud.streaming.*

But we should probably document all of these:

• gcloud.bigquery.query
• gcloud.datastore.helpers - unless there's nothing in here useful to users.
• gcloud.environment_vars
• gcloud.iterator - unless it's thoroughly documented by its downstream clients.
• gcloud.storage.batch

[dhermes]

Everything except gcloud.iterator was documented in the latest commit. It definitely should not be user facing, I'm not sure why we made it public.

[theacodes]

Cool, LGTM.