'Create a dictionary with all metadata for the content.opf
file properly escaped.'

def content_metadata(self):

    writing_mode = self.config.epub_writing_mode
    metadata = super(Epub3Builder, self).content_metadata()
    metadata['description'] = self.esc(self.config.epub_description)
    metadata['contributor'] = self.esc(self.config.epub_contributor)
    metadata['page_progression_direction'] = PAGE_PROGRESSION_DIRECTIONS.get(writing_mode)
    metadata['ibook_scroll_axis'] = IBOOK_SCROLL_AXIS.get(writing_mode)
    metadata['date'] = self.esc(datetime.utcnow().strftime('%Y-%m-%dT%H:%M:%SZ'))
    metadata['version'] = self.esc(self.config.version)
    return metadata
