Databricks Data Source Broken

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Issue Summary

Databricks data source does not work. The authorization token for Databricks data source needs to be converted into a byte string as it currently raises TypeError: a bytes-like object is required, not 'str'
Calling .encode() to transform to a byte string makes the data source work.

redash/redash/query_runner/databricks.py

Lines 51 to 52 in b089f5f

	auth = base64.b64encode("token:" + password)
	transport.setCustomHeaders({"Authorization": "Basic " + auth})

Steps to Reproduce

1. Create a Databricks data source
2. Run test connection and you will get the message: a bytes-like object is required, not 'str'

Any other info e.g. Why do you consider this to be a bug? What did you expect to happen instead?

Technical details:

• Redash Version: master
• Browser/OS: Chrome
• How did you install Redash: Docker development environment