Dsub

Python 3 is now part of automated testing.
All unit and integration tests are now run with Python 2.7 and Python 3.7.

The `google` provider is no longer included in automated tests.

Specific changes in this release include:

- dstat
- Separate recursive input/output from input/output fields..
- Fix `YAMLLoadWarning` that was being emitted.
- dsub
- Experimental: generate 32 character UUID job ids with `--unique-job-ids` flag.
- `local` provider updates:
- Ensure runner-log.txt is written as text.
- `google-v2` provider updates:
- Add timestamps in .log files.
- Test updates:
- Remove the `google` provider from automated tests.
- Fix the way that the project ID is discovered for Python 3.
- Increase concurrency and optionally disable Python module tests.

This release includes one change:

- `google-v2` is now the default provider.

**Note**:
This is the last planned release with `google` as the default provider.
The new default provider will be `google-v2`.

This release includes:
- `google-v2` provider updates:
- `--disk-type` option added.
- `--service-account` option added.
- Fix `dstat` to find jobs submitted with user-ids containing non-alphanumeric non-hyphen characters.
- Fix `dstat` to better handle operations with no actions.

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.