I upgraded from 3.1.6 to 3.1.8 via "composer update" this morning. After the update the site returned this error message (and only this error message):
Fatal error: Interface 'Flushable' not found in [...] /framework/view/SSViewer.php on line 566
The site has the userforms and nyeholt/news modules installed.
The only mention of this error I can find on the net is in an IRC chat log and is of no use. Has anyone else experienced this? What was done to fix it?
Thanks