Error when an (image) upload’s mime type is unsupported #14366

Job	Run time
Core running from build / Core running from build / Linux	59s
Core running from src / Core running from src / Linux	55s
Core running from build / Core running from build / Windows	52s
Core running from src / Core running from src / Windows	59s
Core running from build / Core running from build / MacOS	58s
Core running from src / Core running from src / MacOS	1m 9s
Gutenberg running from src / Gutenberg running from src / Linux	1m 6s
Gutenberg running from build / Gutenberg running from build / Linux	1m 7s
Gutenberg running from build / Gutenberg running from build / Windows	53s
Gutenberg running from src / Gutenberg running from src / Windows	52s
Gutenberg running from src / Gutenberg running from src / MacOS	1m 9s
Gutenberg running from build / Gutenberg running from build / MacOS	1m 8s
Slack Notifications	1s
Failed workflow tasks	1s
	12m 9s

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