epubcheck error (Illegal character in path segment: space is not allowed)

[claell]

After fixing #70, I now ran into another error.

Apparently, images are not allowed to have spaces in their file names in order to pass the check.

Now, I can surely just use images without spaces.

However, is it sensible to make tex4ebook do some work automatically (like replacing spaces by underscores, for example)?

[michal-h21]

I think it is better to not use spaces in filenames, however I will take a look into this after my vacations.