BigQuery builds seem to be very broken

[dhermes]

e.g.

• https://circleci.com/gh/GoogleCloudPlatform/google-cloud-python/1960
• https://circleci.com/gh/GoogleCloudPlatform/google-cloud-python/1963

There are many more in the last 48 hours (sorry I don't have time to gather them all right now).

We should diagnose and fix ASAP.

[dhermes]

This somehow fixed itself like magic (I made a small PR #3468 that doesn't seem big enough to have fixed these breakages)

[tseaver]

#3468 explicitly fixed the breakage in test_dump_table_w_public_data. The one in test_list_tables might be an eventual-consistency issue?