Comment 1 for bug 1597868

Check Book does not perform schema checks, which is what checking for
missing attributes is. Schema checks are useless. The only
piece of software on the *planet* that cares that <img> tags have alt
attributes is a schema checker, in this case epubcheck. No actual book
reading software will give two hoots about whether an <img> tag has a
missing alt attribute or an empty alt attribute.

Schema checking is a waste of everyone's time and energy and I have no
interest in helping perpetuate it.

 status wontfix