scripts: Better warning for getting reg.py #611

Job	Run time
windows-arm64	1m 16s
android (armeabi-v7a)	56s
android (arm64-v8a)	50s
chromium	1m 48s
generate_source	26s
reuse	8s
build_and_test (Debug, ubuntu-20.04)	1m 12s
build_and_test (Debug, ubuntu-22.04)	1m 10s
build_and_test (Debug, windows-latest)	2m 42s
build_and_test (Debug, macos-latest)	1m 1s
build_and_test (Release, ubuntu-20.04)	1m 34s
build_and_test (Release, ubuntu-22.04)	1m 36s
build_and_test (Release, windows-latest)	2m 30s
build_and_test (Release, macos-latest)	59s
	18m 8s

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