Return a file: URL that probably points to the basedir.

        This is used as a halfway sane default when the base URL is not
        provided; not perfect, but should work in most cases.

def getBaseUrl(self):
        '''Return a file: URL that probably points to the basedir.

        This is used as a halfway sane default when the base URL is not
        provided; not perfect, but should work in most cases.'''
        components = util.splitpath(os.path.abspath(self.basepath))
        url = '/'.join([url_quote(component, '') for component in components])
        return 'file:///' + url + '/'