update-manager fails silently

[Peter Stalman]

When I run the "Software Updater" from the menu, and the click "Upgrade..." it will fail without any notification.

If I run it from the terminal, I get the reason why:

```
$ sudo update-manager
[sudo] password for user:
Checking for a new Ubuntu release
Please install all available updates for your release before upgrading.
```

This is the same error as when I run:

```
$ sudo do-release-upgrade
Checking for a new Ubuntu release
Please install all available updates for your release before upgrading.
```

I would expect the GUI should return this error in a dialog box instead of just exiting silently.

```
$ lsb_release -rd
Description: Ubuntu 18.04.5 LTS
Release: 18.04
```

```
$ apt-cache policy update-manager
update-manager:
  Installed: 1:18.04.11.13
  Candidate: 1:18.04.11.13
  Version table:
 *** 1:18.04.11.13 500
        500 http://ca.archive.ubuntu.com/ubuntu bionic-updates/main amd64 Packages
        500 http://ca.archive.ubuntu.com/ubuntu bionic-updates/main i386 Packages
        100 /var/lib/dpkg/status
     1:18.04.11 500
        500 http://ca.archive.ubuntu.com/ubuntu bionic/main amd64 Packages
        500 http://ca.archive.ubuntu.com/ubuntu bionic/main i386 Packages
```

[Akbarkhon Variskhanov (kbar)]

Are you offered to install some updated software? Because on my end, Software Updater is offering me to install updated software first. There is nothing about upgrades. As soon as it's done updating, a new window appears notifying me of Ubuntu 20.04 LTS. It has three buttons:
<Settings> <Upgrade...> <OK>

1. If there is updated software available, Software Updated pops up.
2. Then it checks for upgrades.

If you run sudo apt update in Terminal, what do you see? Are you offered to update some packages? If yes then everything is working as intended.

[Akbarkhon Variskhanov (kbar)]

I cannot seem to reproduce this bug. Could you please describe the steps needed to reproduce it?

Also, did you get notified of updates before that? Does that happen every time you click on "Upgrade"? What happens before you click on it?

[Peter Stalman (sarke)]

So yes, I've updated all the available packages and the software updater offers to upgrade to the next major release.

I see the three buttons as you described:

<Settings> <Upgrade...> <OK>

I click <Upgrade...> and nothing happens.

The reason WHY nothing happens is a different error, created by a package being held back.

However, it does fail, and it really doesn't.matter why it fails, I think it needs to inform the user that it did indeed fail and offer some sort of error message as to why.

[Akbarkhon Variskhanov (kbar)]

You're not even asked to authenticate?

[Launchpad Janitor (janitor)]

[Expired for update-manager (Ubuntu) because there has been no activity for 60 days.]