Plesk 11.5 MU#11 - Bad Gateway 502 - PleskFatalException

[netsetter]

It happens with every update since 11.5.x:

Internal error.
ERROR: PleskFatalException: Unable to connect to database: mysql_connect(): No such file or directory (auth.php:139)

So far I always could ignore this error, but this time, after installing MU#11, I am unable to login to plesk panel, it now says:

502 Bad Gateway
nginx

Any ideas?


Update: I'm able to login again, seems that I had to wait a few minutes, now the Bad Gateway error isn't showing up anymore.