The following error is shown during Plesk microupdates installation or upon executing the command
service psa startallor
service psa stopall:
CONFIG_TEXT: /usr/lib/plesk-9.0/psa_service: line 1537: : bad substitution
Plesk Onyx 17.8 is installed on Debian 9 or Ubuntu 18.
Antivirus is set to 'none' at Tools & Settings > Mail Server Settings
The issue is submitted as a bug PPPM-8165 which is planned to be fixed in one of the future Plesk updates.
The error can be safely ignored as it does not affect Plesk functionality.
As a workaround, set Antivirus other than 'None' at Tools & Settings > Mail Server Settings before installing Plesk Microupdates.
Note: Antivirus should be installed on the server.