Created a new importer not attached to a content type. In Settings for HTTP Fetcher "Use PubSubHubbub" is unchecked.
When I try to create the importer (supplying an url for it) under domain/import it fails with the a curl related error message:
"Call to undefined function curl_init() in /var/www/referate/international/sites/all/modules/feeds/libraries/PuSHSubscriber.inc on line 74"
This means the function subscribe in PuSHSubscriber.inc is called even if the use PubSubHubbub setting is not activated and the feed in question definitely does not provide anything related to PubSubHubbub.
1.) The errournous call must be fixed
2.) The included lib should be protected against a missing curl lib settup in php