Comment 6 for bug 256920

A lot of /etc files were apparently removed. This also prevents apache2 from restarting. You might need to purge/reinstall apache2, apache2-common... to restore the needed conf files like /etc/apache2/envvars.

It might be sufficient to just recreate the file manually :

$ sudo cat /etc/apache2/envvars << EOD
export APACHE_RUN_USER=www-data
export APACHE_RUN_GROUP=www-data
export APACHE_PID_FILE=/var/run/apache2.pid
EOD
$

However I would be surprised if envvars was the only file missing.