[GCP-5388] Storage: Blob.exists() does not work within Batch context

[IlyaFaer]

IPR: 5388

Not very beautiful (that's how I see), but looks like it's the only easy solution. For now, exists() don't do requests while in batch context. It only adds request into list, which will be processed on exiting batch context. So exists() returns True after adding request into batch list, but it doesn't wait for requests to be processed. I've added object to pass it as target object into request (it will bind future request to this object) and to get result after exiting context

[sumit-ql]

Overall, solution looks good, just couple of comments related to test coverage:

1. Are we having a test where we are covering the case : "current.batch is not None".
2. We should also have tests for FutureBoolResult class.

[sumit-ql]

Is there any changes in nox file, if not, please remove this file from the the PR.

[emar-kar]

LGTM.
Checked noxfile chgs and as I see there was a correction to pass black session.

[mf2199]

LGTM.
Checked noxfile chgs and as I see there was a correction to pass black session.

@emar-kar You probably meant, blacken session.

[IlyaFaer]

@mf2199, @emar-kar, @sumit-ql, I think we have some problems with our master, 'cause in PPR I don't have changes in noxfile. We have bash-script for master sync, use it (watch for paths and repo names - yours can be different)