apport mistakenly duplicates bugs with similar but not identical python stacktraces

[Jean-Baptiste Lallement]

apport duplicates bug 1774131 and bug 1269397 with similar but different python stack traces.

bug 1269397
update-manager crashed with AttributeError in resize_to_standard_width(): 'NoneType' object has no attribute 'get_resolution'

bug 1774131
update-manager crashed with AttributeError in resize_to_standard_width(): 'UpdateManager' object has no attribute 'signal_changed'

The following bucket also collect both traces based only on the first part of the trace: update-manager (AttributeError) <lambda> → resize_to_standard_width

https://errors.ubuntu.com/problem/76971c92f002117650d5630a6b13a8ba683e2343

ProblemType: Bug
DistroRelease: Ubuntu 18.10
Package: apport 2.20.10-0ubuntu2
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportLog:

ApportVersion: 2.20.10-0ubuntu2
Architecture: amd64
CurrentDesktop: ubuntu:GNOME
Date: Wed May 30 09:34:27 2018
InstallationDate: Installed on 2014-07-15 (1414 days ago)
InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Alpha amd64 (20140520)
PackageArchitecture: all
SourcePackage: apport
UpgradeStatus: Upgraded to cosmic on 2018-03-24 (66 days ago)

[Brian Murray (brian-murray)]

Looking at a couple of crash reports from different releases in the bucket we can see the DuplicateSignature is the same.

https://errors.ubuntu.com/oops/0df57774-6459-11e8-b827-fa163ed44aae

DuplicateSignature
/usr/bin/update-manager:AttributeError:<lambda>:resize_to_standard_width

https://errors.ubuntu.com/oops/b5eba116-1aca-11e8-aaf0-fa163e839e11

DuplicateSignature
/usr/bin/update-manager:AttributeError:<lambda>:resize_to_standard_width