Comment 2 for bug 1715682

Hi David,
there are a few things in your log that could be related.
First of all - the server has to be restarted on upgrade to pick up th enew code, that restart seems to fail.
But also there is an issue in postinst trying to enable all modules you had.

From the log (1):
info: Executing deferred 'a2enconf javascript-common' for package javascript-common
ERROR: Conf javascript-common does not exist!
dpkg: error processing package apache2 (--configure):
 subprocess installed post-installation script returned error exit status 1

Please check if you have "javascript-common" installed.
If you do so please check a2enconf manually and why it might fail.

From the log (2):
[Thu Sep 07 14:41:48.390332 2017] [mpm_prefork:notice] [pid 11706] AH00163: Apache/2.4.7 (Ubuntu) configured -- resuming normal operations
[Thu Sep 07 14:41:48.390552 2017] [core:notice] [pid 11706] AH00094: Command line: '/usr/sbin/apache2'
[Thu Sep 07 15:36:28.451387 2017] [mpm_prefork:notice] [pid 11706] AH00171: Graceful restart requested, doing restart
apache2: Syntax error on line 140 of /etc/apache2/apache2.conf: Syntax error on line 2 of /etc/apache2/mods-enabled/mpm_prefork.load: Cannot load /usr/lib/apache2/modules/mod_mpm_prefork.so into server: /usr/lib/apache2/modules/mod_mpm_prefork.so: undefined symbol: ap_set_listencbratio
[Thu Sep 07 16:42:44.526369 2017] [mpm_prefork:notice] [pid 1349] AH00163: Apache/2.4.18 (Ubuntu) configured -- resuming normal operations
[Thu Sep 07 16:42:44.558239 2017] [core:notice] [pid 1349] AH00094: Command line: '/usr/sbin/apache2'

The times there are odd, maybe you fixed this already between 15:36 and 16:42?
But from what I found in the net about that it might be an issue in the http config.
If you have modified that you might consider saving your custom config, restart with the one Ubuntu provides [1] and then step by step reenable your changes until you find what broke it.

[1]: https://askubuntu.com/questions/66533/how-can-i-restore-configuration-files