const runtime.runeError

5 uses

	runtime (current package)
		string.go#L262: 		v = runeError
		utf8.go#L9: 	runeError = '\uFFFD'     // the "error" Rune or "Unicode replacement character"
		utf8.go#L64: 		return runeError, k + 1
		utf8.go#L99: 	return runeError, k + 1
		utf8.go#L116: 		r = runeError