When testing #10005 I got a warning from Make to EXPECT ERRORS! when compiling with DISABLE_MODULE=periph_gpio_irq.
This warning is needless since the feature periph_gpio_irq is optional and thus excluding it should not throw any errors. Even more, if it throws errors then there is a bug that should neither be expected nor in the code at all.

Meaning if a feature added with FEATURES_OPTIONAL is excluded again with DISABLE_MODULE, this warning should not be printed.