Plesk upgrade failed with following error on Ubuntu 12.04:
The following packages have unmet dependencies
plesk-core : Depends: libapache2-mod-perl2 but it is not going to be installed
Depends: libapache2-mod-python but it is not going to be installed
Unable to reconfigure webspace:
apache2: Syntax error on line 140 of /etc/apache2/apache2.conf: Syntax error on line 1 of /etc/apache2/mods-enabled/fcgid.load: Cannot load /usr/lib/apache2/modules/mod_fcgid.so into server: /usr/lib/apache2/modules/mod_fcgid.so: undefined symbol: unixd_config
Apache 2.4 version is installed on the server:
Server version: Apache/2.4 (Unix)
During upgrade, Plesk needs to install Apache from official repositories, but packages conflict with Apache 2.4.
Downgrade apache to 2.2 or uninstall it and rerun plesk upgrade.
Ubuntu 12.04 and older supports Apache 2.2 version.