update-manager crashed with AttributeError in update(): 'NoneType' object has no attribute 'saveDistUpgrade'

[e-evil]

Errors Bucket:
https://errors.ubuntu.com/bucket/?id=/usr/bin/update-manager%3AAttributeError%3A/usr/bin/update-manager%40121%3Astart_update%3Astart_available%3Arefresh_cache%3Aupdate

crashed during checking for updates

ProblemType: CrashDistroRelease: Ubuntu 14.10
Package: update-manager 1:14.10.2
ProcVersionSignature: Ubuntu 3.16.0-4.9-generic 3.16.0-rc5
Uname: Linux 3.16.0-4-generic x86_64
ApportVersion: 2.14.4-0ubuntu2
Architecture: amd64
CrashCounter: 1
CurrentDesktop: Unity
Date: Mon Jul 21 20:29:34 2014
EcryptfsInUse: Yes
ExecutablePath: /usr/bin/update-manager
GsettingsChanges:
 b'com.ubuntu.update-manager' b'first-run' b'false'
 b'com.ubuntu.update-manager' b'launch-time' b'1405963770'
InstallationDate: Installed on 2014-07-19 (1 days ago)
InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20140719)
InterpreterPath: /usr/bin/python3.4
PackageArchitecture: all
ProcCmdline: /usr/bin/python3 /usr/bin/update-manager --no-update
PythonArgs: ['/usr/bin/update-manager', '--no-update']SourcePackage: update-manager
Title: update-manager crashed with AttributeError in update(): 'NoneType' object has no attribute 'saveDistUpgrade'
UpgradeStatus: No upgrade log present (probably fresh install)
UserGroups: adm cdrom dip lpadmin plugdev sambashare sudo

[Brian Murray (brian-murray)]

The command line option of "--no-update" (/usr/bin/python3 /usr/bin/update-manager --no-update) might explain cache being undefined.

[Remco Brenninkmeijer (requist1)]

I was having the same problem but I could not run the above command, it got stuck with only a (I assume) non-relevant warning about a deprecated button use.
Using aptitude it first gave me a warning about unable to update and propose several keeps, but after accepting the keeps it gave an other message about broken packages which it could fix. After this no keeps and it could do a normal update.
After this, update still did not run but then I discovered there where mere update processes running at the same time. Killing them enabled me to run update and the problem is gone.

So for me the real problem looked to be the broken packages but unfortunately the broken packages were not logged and I have not noted them down. For the command line option to run it might give more info after killing the running update processes.

[Greg Soltis (gsoltis)]

What worked for me was clearing files out of /var/lib/dpkg/updates. ubuntu 16.04. UpdateManager.py, in refresh_cache, is hiding the underlying exception from trying to open the cache. Opening the cache asserts that there are no files in /var/lib/dpkg/updates that fit a certain regex, and that was what was failing.