[Merge] lp:~brian-murray/ubuntu-archive-tools/phased-updater-traceback2 into lp:ubuntu-archive-tools

[Brian Murray]

This fixes another traceback.

Traceback (most recent call last):
  File "/home/ubuntu-archive/ubuntu-archive-tools/phased-updater", line 605, in <module>
    main()
  File "/home/ubuntu-archive/ubuntu-archive-tools/phased-updater", line 571, in main
    generate_html_report(releases, issues)
  File "/home/ubuntu-archive/ubuntu-archive-tools/phased-updater", line 160, in generate_html_report
    buckets[rname][pub_source]['previous_pup']
KeyError: 'previous_pup'
                                                                                                
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https://code.launchpad.net/~brian-murray/ubuntu-archive-tools/phased-updater-traceback2/+merge/210518
Your team Ubuntu Package Archive Administrators is requested to review the proposed merge of lp:~brian-murray/ubuntu-archive-tools/phased-updater-traceback2 into lp:ubuntu-archive-tools.