Originally reported by @pbokoc:

There are a couple problems with the entities.adoc file that docscii currently creates and that serves as a replacement for Book_Name.ent in DocBook.

• Let's call it attributes.adoc instead, since that's what's adoc calls these things.
• Docscii currently adds a {nbsp} attribute into that file even though the original doesn't contain that, and tries to define it as a single space, which doesn't seem to work at all. ASCIIDoc actually has a built-in {nbsp} attribute, so let's use that instead of trying to define it again and breaking it in the process. In other words, docscii should continue converting   into {nbsp} within books, but it should stop adding that attribute into the attribute file.