Dsub

This release includes:

- `dsub`
- When tasks are retried (based on use of the `--retries` flag), output messages are now more informative.
- [bash](https://hub.docker.com/_/bash) image can now be used with the `local` and `google-v2` providers (updated Docker entrypoints to use `/usr/bin/env bash` instead of `/bin/bash`)
- `google-v2` provider updates:
- `--nvidia-driver-version` parameter can now be used to specifiy the NVIDIA driver version to use when attaching an NVIDIA GPU accelerator.
- log files are copied locally on the VM before upload to GCS. This avoids `ResumableUploadAbortException` copying large logs.

- `dstat`
- `script` and `script-name` now appears in `dstat --full` output.
- `pyyaml` version updated to latest version allowing Python3.7 support.

This release includes:
- `google-v2` provider:
- `--min-ram` and `--min-core` parameters can now be used to automatically select one of the [Compute Engine Custom Machine Types](https://cloud.google.com/compute/docs/machine-types#custom_machine_types).
- `--mount` a persistent disk created from a [Compute Engine Image](https://cloud.google.com/compute/docs/images)
- Prefixes like "Execution failed: action \<n\>" removed from status messages in `dstat`.
- `local` provider:
- `--mount` a local directory
- Add Hong Kong zones.

This release includes:

- `google`:
- A large deprecation WARNING will now be emitted when using the `google` provider.
- `google-v2`
- Exit with error if logging fails.
- Better messaging on failures.
- Bug fixes for exception handling in `ddel` jobs
- `local`:
- Better messaging on logging failures.

This release includes:

* Support for [Requester Pays buckets](https://cloud.google.com/storage/docs/requester-pays) via the new `--user-project` option (`google-v2` and `local` providers)
* Fixes `dstat ... --limit` off-by-one bug

This release includes:

- Documentation updates noting the deprecation of the google provider.
- `google-v2` provider updates:
- `--log-interval` flag to configure the amount of time to sleep between copying log files from the pipeline to the logging path.
- Adding `google-v2` specific elements to `dstat` output.
- `--ssh` flag to start an SSH container in the background, allowing you to inspect the runtime
environment of your job's container in real time.
- Experimental support for gcsfuse through the `--mount` flag.
- `local` provider updates:
- Add support for Docker images with entrypoints

This release includes:

- Experimental Python 3 support.
- Improvements to retry logic on transient HTTP errors.
- `google-v2` provider:
- `dstat` fixes:
- Fix for "ok" event in the wrong order.
- Decreased operations.list page size to work around quota exception.
- Fix for 'pulling-image' event discovery.
- `dsub` fixes:
- Fix pipeline hang in localization/delocalization on error on multi-core VMs