private static String throwBadUtf8(int value, int offset) {
    throw new IllegalArgumentException(
        "bad utf-8 byte " + Hex.u1(value) + " at offset " + Hex.u4(offset));
  }
Helper for {@link #utf8BytesToString}, which throws the right exception for a bogus utf-8 byte.

@param value the byte value
@param offset the file offset
@return never
@throws IllegalArgumentException always thrown
android/android_framework/dex-maker/src/main/java/com/android/dx/rop/cst/CstString.java