[Bug 1851040] [NEW] "No valid sources.list entry found" during attempt to upgrade from Eoan to Focal

[Norbert]

Public bug reported:

Steps to reproduce:
1. Have Ubuntu 19.10 installed (edition really does not matter, but tested on MATE)
2. Run `update-manager -d -c `
3. Follow wizard, confirm upgrade to 20.04 LTS

Expected results:
* upgrade is started and ended successfully

Actual results:
* upgrade is not started, have the following window  

```
No valid sources.list entry found

While scanning your repository information no entry about disco could be
found.

An upgrade might not succeed.

Do you want to continue anyway?

No Yes
```

Terminal output is the following:

```
$ update-manager -d -c 
WARNING:root:can not import unity GI Namespace Dbusmenu not available
Checking for a new Ubuntu release
Checking for a new Ubuntu release
/usr/lib/python3/dist-packages/DistUpgrade/DistUpgradeFetcher.py:23: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
  from gi.repository import Gtk, Gdk
/usr/lib/python3/dist-packages/DistUpgrade/ReleaseNotesViewerWebkit.py:33: PyGIWarning: WebKit2 was imported without specifying a version first. Use gi.require_version('WebKit2', '4.0') before import to ensure that the right version gets loaded.
  from gi.repository import WebKit2 as WebKit
error: XDG_RUNTIME_DIR not set in the environment.
authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg' 
extracting 'focal.tar.gz'

```

ProblemType: Bug
DistroRelease: Ubuntu 19.10
Package: ubuntu-release-upgrader-core 1:19.10.15
ProcVersionSignature: Ubuntu 5.3.0-19.20-generic 5.3.1
Uname: Linux 5.3.0-19-generic x86_64
ApportVersion: 2.20.11-0ubuntu8.1
Architecture: amd64
CrashDB: ubuntu
CurrentDesktop: MATE
Date: Sat Nov  2 16:51:48 2019
InstallationDate: Installed on 2019-10-19 (14 days ago)
InstallationMedia: Ubuntu-MATE 19.10 "Eoan Ermine" - Release amd64 (20191017)
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to eoan on 2019-11-02 (0 days ago)
VarLogDistupgradeAptlog:
 Log time: 2019-11-02 16:49:52.579694
 Log time: 2019-11-02 16:49:56.716523
VarLogDistupgradeTermlog:

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


** Tags: amd64 apport-bug dist-upgrade eoan iso-testing

-- 
You received this bug notification because you are a member of Ubuntu
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Ubuntu.
https://bugs.launchpad.net/bugs/1851040

Title:
  "No valid sources.list entry found" during attempt to upgrade from
  Eoan to Focal

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

Bug description:
  Steps to reproduce:
  1. Have Ubuntu 19.10 installed (edition really does not matter, but tested on MATE)
  2. Run `update-manager -d -c `
  3. Follow wizard, confirm upgrade to 20.04 LTS

  Expected results:
  * upgrade is started and ended successfully

  Actual results:
  * upgrade is not started, have the following window  

  ```
  No valid sources.list entry found

  While scanning your repository information no entry about disco could
  be found.

  An upgrade might not succeed.

  Do you want to continue anyway?

  No Yes
  ```

  Terminal output is the following:

  ```
  $ update-manager -d -c 
  WARNING:root:can not import unity GI Namespace Dbusmenu not available
  Checking for a new Ubuntu release
  Checking for a new Ubuntu release
  /usr/lib/python3/dist-packages/DistUpgrade/DistUpgradeFetcher.py:23: PyGIWarning: Gtk was imported without specifying a version first. Use gi.require_version('Gtk', '3.0') before import to ensure that the right version gets loaded.
    from gi.repository import Gtk, Gdk
  /usr/lib/python3/dist-packages/DistUpgrade/ReleaseNotesViewerWebkit.py:33: PyGIWarning: WebKit2 was imported without specifying a version first. Use gi.require_version('WebKit2', '4.0') before import to ensure that the right version gets loaded.
    from gi.repository import WebKit2 as WebKit
  error: XDG_RUNTIME_DIR not set in the environment.
  authenticate 'focal.tar.gz' against 'focal.tar.gz.gpg' 
  extracting 'focal.tar.gz'

  ```

  ProblemType: Bug
  DistroRelease: Ubuntu 19.10
  Package: ubuntu-release-upgrader-core 1:19.10.15
  ProcVersionSignature: Ubuntu 5.3.0-19.20-generic 5.3.1
  Uname: Linux 5.3.0-19-generic x86_64
  ApportVersion: 2.20.11-0ubuntu8.1
  Architecture: amd64
  CrashDB: ubuntu
  CurrentDesktop: MATE
  Date: Sat Nov  2 16:51:48 2019
  InstallationDate: Installed on 2019-10-19 (14 days ago)
  InstallationMedia: Ubuntu-MATE 19.10 "Eoan Ermine" - Release amd64 (20191017)
  PackageArchitecture: all
  SourcePackage: ubuntu-release-upgrader
  Symptom: ubuntu-release-upgrader
  UpgradeStatus: Upgraded to eoan on 2019-11-02 (0 days ago)
  VarLogDistupgradeAptlog:
   Log time: 2019-11-02 16:49:52.579694
   Log time: 2019-11-02 16:49:56.716523
  VarLogDistupgradeTermlog:

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