Ubuntu – Unable to upgrade from 14.04 to 16.04. Could not calculate the upgrade. An unresolvable problem occurred while calculating the upgrade


Unable to upgrade from 14.04 to 16.04. I'm trying sudo do-release-upgrade and it fails with the following error:

Calculating the changes

Could not calculate the upgrade 

An unresolvable problem occurred while calculating the upgrade. 

This can be caused by: 
* Upgrading to a pre-release version of Ubuntu 
* Running the current pre-release version of Ubuntu 
* Unofficial software packages not provided by Ubuntu 

If none of this applies, then please report this bug using the 
command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. 

Restoring original system state

/var/log/dist-upgrade/main.log https://www.dropbox.com/s/3gf1tg8uxmn75jq/main.log?dl=0

I don't understand why package manager can not resolve this and what package is the source of this problem.

Appreciate any help.

Best Answer

I encountered the same problem using the 'About this computer' > 'Upgrade' route on a fully updated 14.04 LTS system. I have software from quite a few alternative repositories, which several posts suggest might have caused the problem.

grep Broken /var/log/dist-upgrade/apt.log reported 163 lines, many of which were gnuplot related. I note a few other posts that reported gnuplot as a problem.

I deleted the two gnuplot packages installed on my system using Synaptic and then closed Synaptic. Interestingly, when filtering with 'installed(upgradeable)' in Synaptic, only these two packages showed up (gnuplot and gnuplotX11) and both had an exclamation mark in the checkbox.

Then do-release-upgrade worked.