Upgrade to 0.17.0rc2

[beckjake]

Fixes #78
Fixes #81 (sort of...)

Prevent users from setting database just about anywhere. It would have been nice to make database and schema equivalent, like in real spark, but that requires some ugly hacks on the dbt-core end.

In the longer term, it would be nice to expose more things about config to plugins. Adapter specific configs can add new fields, but they can't remove them, and they can't even really check on them to see if they make sense because the builtin fields are examined before the adapter ones are considered. I'm not sure how exactly we could support such behavior in the dataclasses/hologram paradigm, but we can think about it more. Instead, the spark adapter now checks when relations are built, and errors out then. I don't think it's ideal, but it happens before dbt starts really running (when it's examining the manifest for what schemas to create) so at least there's that.

This also upgrades the plugin to 0.17.0rc1 0.17.0rc2 in anticipation of the dbt 0.17.0 release - 0.17.0 support should just be a bumpversion away.

[jtcohen6]

I took for a spin locally with containerized Spark and all worked as expected. I tested with overriding generate_schema_name (as expected) and generate_database_name (no effect). I left a few comments around the specific error messages to return.

Weirdly, when I try to test against Databricks, I'm seeing only this error:

Encountered an error:
Runtime Error
  Runtime Error
    Database Error

This is before it even tries to connect to the cluster. Here are the last few lines from the traceback:

File "/Users/jerco/dev/product/spark/env/lib/python3.7/site-packages/dbt_core-0.17.0rc1-py3.7.egg/dbt/task/runnable.py", line 473, in list_schemas
    for s in adapter.list_schemas(database_quoted)
  File "/Users/jerco/dev/product/spark/env/lib/python3.7/site-packages/dbt_core-0.17.0rc1-py3.7.egg/dbt/adapters/sql/impl.py", line 233, in list_schemas
    kwargs={'database': database}
  File "/Users/jerco/dev/product/spark/env/lib/python3.7/site-packages/dbt_core-0.17.0rc1-py3.7.egg/dbt/adapters/base/impl.py", line 981, in execute_macro
    self.release_connection()
  File "/usr/local/Cellar/python/3.7.7/Frameworks/Python.framework/Versions/3.7/lib/python3.7/contextlib.py", line 130, in __exit__
    self.gen.throw(type, value, traceback)
  File "/Users/jerco/dev/product/spark/dbt-spark/dbt/adapters/spark/connections.py", line 201, in exception_handler
    raise dbt.exceptions.RuntimeException(str(exc))
dbt.exceptions.RuntimeException: Runtime Error
  Runtime Error
    Database Error

[jtcohen6]

For posterity: the issue above was actually a matter of my Databricks token having expired. (My b!) We're adding a more descriptive error (and helpful reminder) for the next time this happens.

[beckjake]

I'm going to hold off on merging this until dbt 0.17.0 is officially out - once that happens I'll run the appropriate bumpversion commands and push to this branch.