[Bug 1901881] [NEW] dist upgrade didnt work

[Awaken Kraken]

Public bug reported:

Trying to run the upgrader resulted in this error


```
Could not calculate the upgrade

An unresolvable problem occurred while calculating the upgrade.

 This was caused by:
 * Upgrading to a pre-release version of Ubuntu
This is most likely a transient problem, 
please try again later.
If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If you want to investigate this yourself the log files in '/var/log/dist-upgrade' will contain details about the upgrade. Specifically, look at 'main.log' and 'apt.log'.
```

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubuntu-release-upgrader-core 1:18.04.40
ProcVersionSignature: Ubuntu 5.4.0-52.57~18.04.1-generic 5.4.65
Uname: Linux 5.4.0-52-generic x86_64
NonfreeKernelModules: nvidia_modeset nvidia
ApportVersion: 2.20.9-0ubuntu7.18
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: ubuntu:GNOME
Date: Wed Oct 28 07:00:25 2020
InstallationDate: Installed on 2020-10-28 (0 days ago)
InstallationMedia: Ubuntu 18.04.5 LTS "Bionic Beaver" - Release amd64 (20200806.1)
PackageArchitecture: all
ProcEnviron:
 TERM=xterm-256color
 PATH=(custom, no user)
 XDG_RUNTIME_DIR=<set>
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: ubuntu-release-upgrader
UpgradeStatus: Upgraded to bionic on 2020-10-28 (0 days ago)
VarLogDistupgradeTermlog:

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: amd64 apport-bug bionic dist-upgrade third-party-packages

-- 
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https://bugs.launchpad.net/bugs/1901881

Title:
  dist upgrade didnt work

Status in ubuntu-release-upgrader package in Ubuntu:
  New

Bug description:
  Trying to run the upgrader resulted in this error

  
  ```
  Could not calculate the upgrade

  An unresolvable problem occurred while calculating the upgrade.

   This was caused by:
   * Upgrading to a pre-release version of Ubuntu
  This is most likely a transient problem, 
  please try again later.
  If none of this applies, then please report this bug using the command 'ubuntu-bug ubuntu-release-upgrader-core' in a terminal. If you want to investigate this yourself the log files in '/var/log/dist-upgrade' will contain details about the upgrade. Specifically, look at 'main.log' and 'apt.log'.
  ```

  ProblemType: Bug
  DistroRelease: Ubuntu 18.04
  Package: ubuntu-release-upgrader-core 1:18.04.40
  ProcVersionSignature: Ubuntu 5.4.0-52.57~18.04.1-generic 5.4.65
  Uname: Linux 5.4.0-52-generic x86_64
  NonfreeKernelModules: nvidia_modeset nvidia
  ApportVersion: 2.20.9-0ubuntu7.18
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: ubuntu:GNOME
  Date: Wed Oct 28 07:00:25 2020
  InstallationDate: Installed on 2020-10-28 (0 days ago)
  InstallationMedia: Ubuntu 18.04.5 LTS "Bionic Beaver" - Release amd64 (20200806.1)
  PackageArchitecture: all
  ProcEnviron:
   TERM=xterm-256color
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to bionic on 2020-10-28 (0 days ago)
  VarLogDistupgradeTermlog:

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