bug#29189: 25.3; Dired does not work with binary filenames

[Eli Zaretskii]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: handa@gnu.org,  vianchielfaura@gmail.com,  29189@debbugs.gnu.org,  
> schwab@suse.de
> Date: Sun, 07 Jan 2018 10:20:06 -0500
> 
> > Input that is from multibyte text can include raw bytes in their
> > multibyte representation.  What is a "non-byte"?
> 
> `λ`?  `é`?  `²`?

These are characters, so they will never end up in the code fragment
that was the subject of this big, because that code deals specifically
with the unprocessed tail of byte stream that could not be decoded.
They will be decoded with the rest of the text before we get to the
code being discussed.

And even if you would like to add there assertion for "cannot happen"
stuff, how would you identify such "non-bytes"?  Their byte sequences
depend on the original encoding, so detecting them sounds like your
favorite Turing stopping problem, no?