[Bug 1805475] [NEW] ubuntu-release-upgrader crashed with AttributeError: '_NamespacePath' object has no attribute 'sort'

[errors.ubuntu.com bug bridge]

Public bug reported:

The Ubuntu Error Tracker has been receiving reports about a problem regarding ubuntu-release-upgrader.  This problem was most recently seen with package version 1:18.04.29, the problem page at https://errors.ubuntu.com/problem/2abac1a6a3ae5c39236650a7254635c02ae02a69 contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports.
If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/.

** Affects: ubuntu-release-upgrader (Ubuntu)
     Importance: Medium
     Assignee: Brian Murray (brian-murray)
         Status: In Progress


** Tags: bionic xenial

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https://bugs.launchpad.net/bugs/1805475

Title:
  ubuntu-release-upgrader crashed with AttributeError: '_NamespacePath'
  object has no attribute 'sort'

Status in ubuntu-release-upgrader package in Ubuntu:
  In Progress

Bug description:
  The Ubuntu Error Tracker has been receiving reports about a problem regarding ubuntu-release-upgrader.  This problem was most recently seen with package version 1:18.04.29, the problem page at https://errors.ubuntu.com/problem/2abac1a6a3ae5c39236650a7254635c02ae02a69 contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports.
  If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/.

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