Get full URI (filepath) for sitemap based on basename.

def sitemap_uri(self, basename):
        """Get full URI (filepath) for sitemap based on basename."""
        if (re.match(r"\w+:", basename)):
            # looks like URI
            return(basename)
        elif (re.match(r"/", basename)):
            # looks like full path
            return(basename)
        else:
            # build from mapping with name appended
            return(self.mapper.default_src_uri() + '/' + basename)