session_start(): Failed to initialize storage module: user (path: )

Hello,

There is a problem when using cleantalk-spam-protect on pantheon’s hosting platform that starting with version 5.72 (it has run fine up through 5.71, which is what we’re still using): after updating (tried with 5.72 and 5.74) everything seems fine at first but after a while the site turns into a “white screen of death” and the following error shows up: session_start(): Failed to initialize storage module: user (path: ) from wp-content/plugins/cleantalk-spam-protect/inc/cleantalk-common.php:119

Pantheon uses a varnish cache, and if I clear the cache this problem will go away for a little while, but shows back up before long. The session can be very active, it does not have to be idle for this to happen (though it will also do it if you leave your session and come back in a bit).

Pantheon also requires the ‘WordPress Native PHP Sessions’ plugin be used, which is surely related – the exact same error is in the troubleshooting section at https://wordpress.org/plugins/wp-native-php-sessions/

The cleantalk plugin is not loaded in mu-plugins, but I’m going to try the workaround suggested there anyways and see if it helps. But could you also look at this and see if whatever changed in 5.72 might be improved or rolled back so that other sites on pantheon and/or running the native php sessions plugin won’t require a similar workaround?

Thanks!