'Process a URL template
There are several variables accessible to the user:
- ${PROXY_URL} will be replaced with the dynamically create proxy\'s url
- ${PROXY_PREFIX} will be replaced with the prefix that may occur'

def url_template(self, url_template):

    if self.attr.SSL_URLS:
        protocol = 'https'
    else:
        protocol = 'http'
    url_template = url_template.replace('${PROTO}', protocol).replace('${HOST}', self.attr.HOST)
    url = url_template.replace('${PROXY_URL}', str(self.attr.proxy_url)).replace('${PROXY_PREFIX}', str(self.attr.proxy_prefix.replace('/', '%2F')))
    return url
