Merge pull request #868 from LaurentMazare/pyo3-0.21 #949

Job	Run time
Rustfmt	10s
Clippy	51s
Test Suite (ubuntu-latest, stable)	1m 35s
Check (ubuntu-latest, stable)	1m 7s
Test Suite (ubuntu-latest, nightly)	1m 44s
Test Suite (macOS-latest, stable)	1m 55s
Check (ubuntu-latest, nightly)	1m 14s
Test Suite (macOS-latest, nightly)	3m 18s
Check (windows-2019, stable)	2m 6s
Check (windows-2019, nightly)	1m 56s
Check (macOS-latest, stable)	2m 1s
Check (macOS-latest, nightly)	2m 21s
	20m 18s

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