##parameters=REQUEST, RESPONSE
from Products.PythonScripts.standard import url_quote
serial = REQUEST.get('variant_serial', None)
if serial:
    variant = context.getVariantBySerial(serial)
    if variant:
        locator = "%s/%s"%(context.absolute_url(), serial)
        REQUEST.set('source_locators', locator)
        sl = variant.addNewSourceLocator(REQUEST, None, context)
        url = context.absolute_url()
        target = 'topicname_variant_source_locator_form'
        query = 'variant_serial=%s&source_locator=%s'%(variant.tm_serial, url_quote(locator))
        RESPONSE.redirect("%s/%s?%s"%(url, target, query))