Fix raw f-string FormatSpecs #531

Job	Run time
Create sdist and Python 3 Wheel	36s
Test Documentation	37s
Create Python 2 Wheel	44s
Test Typing (wheel)	40s
Test Typing (sdist)	48s
Test Package (3.3, sdist)	19s
Test Package (2.7, sdist)	16s
Test Package (2.7, wheel)	17s
Test Package (3.3, wheel)	26s
Test Package (3.8, wheel)	15s
Test Package (3.4, wheel)	17s
Test Package (3.5, sdist)	23s
Test Package (3.7, sdist)	15s
Test Package (3.9, wheel)	23s
Test Package (3.6, wheel)	17s
Test Package (3.7, wheel)	16s
Test Package (3.4, sdist)	21s
Test Package (3.9, sdist)	26s
Test Package (3.6, sdist)	19s
Test Package (3.11, wheel)	27s
Test Package (3.11, sdist)	31s
Test Package (3.10, wheel)	29s
Test Package (3.8, sdist)	19s
Test Package (3.5, wheel)	19s
Test Package (3.10, sdist)	33s
Test Package (3.13, sdist)	29s
Test Package (3.12, sdist)	32s
Test Package (3.14, wheel)	25s
Test Package (3.12, wheel)	26s
Test Package (3.13, wheel)	29s
Test Package (3.14, sdist)	27s
	13m 21s

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