How to convert hex string to string or ubytes? Thanks.

[FrankLike]

On Monday, 5 February 2018 at 06:12:22 UTC, H. S. Teoh wrote:
> On Mon, Feb 05, 2018 at 05:48:00AM +0000, FrankLike via

> 	auto input = "48656c6c6f20776f726c6421";
> 	auto str = input.chunks(2)
> 	                .map!(digits => cast(char) digits.to!ubyte(16))
> 			.array;

But,if the input come from here:

import std.digest.md;
auto hash =md5Of("Some Words");
auto input = cast(string)hexString(hash);

  auto str = input.chunks(2)
  	         .map!(digits => cast(char) digits.to!ubyte(16))
  		 .array;

Then get an error:
core.exception.UnicodeException at src\rt\util\utf.d(292):invalid 
UTF-8 sequence
--------------
0x0041B8E6
0x00419530
0x0040796F

Thanks.