run pytests in parallel

[arvidn]

CI runtime:

CI job	before	after	after / before
Continue with coverage	6m 9s	4m 18s	70%
python tests	2m 59s	1m 35s	53%

[coveralls-official[bot]]

Pull Request Test Coverage Report for Build 9561446642

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 82.773%

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Totals
Change from base Build 9550232150:	0.0%
Covered Lines:	11671
Relevant Lines:	14100

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💛 - Coveralls