Prepare release 1.6.0-rc3 #117

Job	Run time
Start EC2 runner	1m 42s
Install deps and run checks	5m 51s
Run tests / Prepare versions and OS	4s
Run tests / Decide Slack report	1s
Run tests / Start EC2 runner (Linux)	4m 2s
Run tests / Python ${{ matrix.python_version }} (macOS, intel)	0s
Run tests / Python 3.8 (Linux)	53m 34s
Run tests / Python 3.9 (Linux)	52m 16s
Run tests / Python 3.10 (Linux)	53m 49s
Run tests / Stop EC2 runner (Linux)	10s
Run tests / provenance / detect-env	5s
Run tests / provenance / generator	11s
Run tests / Slack report	0s
Run tests / Stop EC2 failure Slack alert	0s
Run tests / provenance / upload-assets	0s
Run tests / provenance / final	1s
Run tests / Build Status (Linux)	1s
Push new tag and branch	7s
Release package and artifacts	15m 20s
Stop EC2 runner	5s
Send Slack notification	12s
	3h 7m 31s

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