Upgrade to focal fails with AttributeError: 'NoneType' object has no attribute 'section' in in DistUpgradeCache.py line 942 when default snap packages are not installed

TESTCASE
1. Branch auto-upgrade-testing and the upgrade profiles and run the command:

sudo python3 -m upgrade_testing.command_line --adt-args -d -s -c <<PATH_TO_PROFILES>>/ubuntu-eoan-focal-desktop-amd64_qemu.yaml --provision --results-dir <<RESULT_DIR>>

TESTCASE 2
1. Install eoan
2. Remove all the snap pacakges but core and core18
3. run in a terminal: do-release-upgrade -d

Error from main.log
2019-12-18 14:57:50,363 DEBUG Start checking for obsolete pkgs
2019-12-18 14:57:50,524 ERROR got exception '<class 'AttributeError'>': 'NoneType' object has no attribute 'section'
NoneType: None
2019-12-18 14:57:50,532 ERROR not handled exception:
Traceback (most recent call last):
  File "/tmp/ubuntu-release-upgrader-oq9n6a1n/focal", line 8, in <module>
    sys.exit(main())
  File "/tmp/ubuntu-release-upgrader-oq9n6a1n/DistUpgrade/DistUpgradeMain.py", line 238, in main
    if app.run():
  File "/tmp/ubuntu-release-upgrader-oq9n6a1n/DistUpgrade/DistUpgradeController.py", line 2082, in run
    return self.fullUpgrade()
  File "/tmp/ubuntu-release-upgrader-oq9n6a1n/DistUpgrade/DistUpgradeController.py", line 2059, in fullUpgrade
    self.doPostUpgrade()
  File "/tmp/ubuntu-release-upgrader-oq9n6a1n/DistUpgrade/DistUpgradeController.py", line 1485, in doPostUpgrade
    if not self.cache.tryMarkObsoleteForRemoval(pkgname, remove_candidates, self.foreign_pkgs):
  File "/tmp/ubuntu-release-upgrader-oq9n6a1n/DistUpgrade/DistUpgradeCache.py", line 241, in wrapper
    res = f(*args, **kwargs)
  File "/tmp/ubuntu-release-upgrader-oq9n6a1n/DistUpgrade/DistUpgradeCache.py", line 942, in tryMarkObsoleteForRemoval
    if pkgname in self and self[pkgname].installed.section == section:
AttributeError: 'NoneType' object has no attribute 'section'

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: ubuntu-release-upgrader-core 1:20.04.7
ProcVersionSignature: User Name 5.3.0-24.26-generic 5.3.10
Uname: Linux 5.3.0-24-generic x86_64
ApportVersion: 2.20.11-0ubuntu14
Architecture: amd64
CrashDB: ubuntu
Date: Wed Dec 18 16:17:08 2019
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to focal on 2019-12-18 (0 days ago)
VarLogDistupgradeAptclonesystemstate.tar.gz:
 Error: command ['pkexec', 'cat', '/var/log/dist-upgrade/apt-clone_system_state.tar.gz'] failed with exit code 127: polkit-agent-helper-1: error response to PolicyKit daemon: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: No session for cookie
 Error executing command as another user: Not authorized

 This incident has been reported.