Include datasets with underscores when listing BigQuery datasets

[k4y3ff]

Pretty sure I ran into the same thing @rsmichaeldunn ran into in #873?

Here's a PR.

[drewbanin]

hey @k4y3ff -- thanks for the PR! This looks great!

I haven't seen this error in the wild yet, so I don't have a great understanding of BigQuery's semantics here. I can dig into this further today, but @rsmichaeldunn also mentioned in the issue:

...and changing the create_schema method to check for the existence of the dataset id in the output of get_existing_schemas instead of using get_dataset

It sounds to me like client.get_dataset(dataset) doesn't return the dataset if it begins with an underscore? Is that consistent with your understanding?

I think it would be really great to add a quick test for this, as the BigQuery client library is updated pretty frequently and this is a super easy thing to miss

[beckjake]

Closing this PR, as this contribution was merged in #1006. Thanks!