Comment 0 for bug 1386434

After running:
sudo do-release-upgrade

the upgrade stops with the message:
>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.

>

In addition, the bug reporting tool also crashes.

None of the suggested causes apply. No further information is available.