By default SimplePie is instanciated with cache = true and cache_location = './cache', which results in a PHP warning as the default directory does not exist in the given context.
Imho it should be the best to use typo3temp or just disable the caching to surpress the warnings...
Warning: ./cache is not writeable. Make sure you've set the correct relative or absolute path, and that the location is server-writable. in /.../typo3conf/ext/rss_display/Resources/Private/PHP/SimplePie/SimplePie.php on line 1379
By default SimplePie is instanciated with
cache = trueandcache_location = './cache', which results in a PHP warning as the default directory does not exist in the given context. Imho it should be the best to usetypo3tempor just disable the caching to surpress the warnings...