Improve unknown usecase error message (#109) #132

Job	Run time
pre-commit	10s
lint	16s
insert-license	13s
lockwood-swiftformat	7s
swifttests / Linux (nightly-main - jammy)	9m 39s
swifttests / Linux (nightly-6.2 - jammy)	9m 45s
swifttests / Linux (6.1 - jammy)	7m 32s
swifttests / Linux (6.0 - jammy)	7m 47s
swifttests / Linux (6.2 - jammy)	6m 55s
swifttests / Embedded Swift SDK for Wasm Build (${{ matrix.swift_version }} - ${{ matrix.os_version }})	0s
swifttests / Swift SDK for Wasm Build (${{ matrix.swift_version }} - ${{ matrix.os_version }})	0s
swifttests / Static Linux Swift SDK Build (${{ matrix.swift_version }} - ${{ matrix.os_version }})	0s
swifttests / Windows (${{ matrix.swift_version }} - windows-2022)	0s
swifttests / macOS (Xcode ${{ matrix.xcode_version }} - ${{ matrix.os_version }} - ${{ matrix.arch }})	0s
soundness / Documentation check	4m 24s
soundness / Python lint check	6s
soundness / YAML lint check	5s
soundness / License headers check	5s
soundness / Unacceptable language check	5s
soundness / Broken symlinks check	4s
soundness / Shell check	40s
soundness / Format check	0s
soundness / API breakage check	0s
	47m 53s

Provide feedback