The docstring in the script does mention.

 * this script will only work when run by members of ~canonical,
   because it's a private team

I thought that might have caused this wasn't sure. I suppose the
easiest fix would be to just give a clearer error message.

I tried running the script after commenting out ~canonical from
AUTHORIZED_TEAMS and the script seems to work fine.
If ~contributor-agreement-canonical is a superset of ~canonical
(is it?) maybe ~contributor-agreement-canonical is enough?

For e.g. the output I got after
AUTHORIZED_TEAMS = [ 'contributor-agreement-canonical' ]

[hydrazine]% ./scan-merge-proposals bzr
loaded existing credentials
https://edge.launchpad.net/1.0/~doxxx/bzr/572092-ignore-dupes/+merge/24543
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~gz/bzr/support_OO_flag_installer/+merge/24484
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~parthm/bzr/538868-message-for-heavy-checkout/+merge/24483
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~bialix/bzr/clean-tree-bzrdir/+merge/24479
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~mbp/bzr/491763-transform-rename-failed/+merge/24474
**** mbp not signed up
    status Needs review

https://edge.launchpad.net/1.0/~jameinel/bzr/remove_zlib_dependency/+merge/24452
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~bialix/bzr/relpath-docstring/+merge/24442
<<<< yay, a member of contributor-agreement-canonical
    status Approved

https://edge.launchpad.net/1.0/~parthm/bzr/181124-ls-short-opts/+merge/24414
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~jbowtie/bzr/fix-515660/+merge/24290
<<<< yay, a member of contributor-agreement-canonical
    status Approved

https://edge.launchpad.net/1.0/~jbowtie/bzr/fix-555439/+merge/24289
<<<< yay, a member of contributor-agreement-canonical
    status Approved

https://edge.launchpad.net/1.0/~jbowtie/bzr/fix-401605/+merge/24284
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~parthm/bzr/549310-mandatory-whoami/+merge/24244
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~mbp/bzr/testsubjects-old/+merge/24188
     mbp already needs to sign
    status Needs review

https://edge.launchpad.net/1.0/~garyvdm/bzr/diff_using_gui/+merge/24076
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~abentley/bzr/transform-commit-full/+merge/24049
**** abentley not signed up
    status Approved

https://edge.launchpad.net/1.0/~gagern/bzr/encodingSafeTests/+merge/23925
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~gagern/bzr/bug560030-include-bash-completion-plugin/+merge/23912
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~parthm/bzr/563646-commit-unicode-message/+merge/23752
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~parthm/bzr/529930-unicode-aliases/+merge/23745
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~jelmer/bzr/split-subsegment/+merge/23611
**** jelmer not signed up
    status Needs review

https://edge.launchpad.net/1.0/~jelmer/bzr/more-colo/+merge/23592
     jelmer already needs to sign
    status Needs review

https://edge.launchpad.net/1.0/~amanica/bzr/rm_dir_with_changed_emigrated_file-129880/+merge/23528
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~gagern/bzr/bug560030-drop-completions/+merge/23224
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~gagern/bzr/bug513322-authors/+merge/23122
<<<< yay, a member of contributor-agreement-canonical
    status Needs review

https://edge.launchpad.net/1.0/~jelmer/bzr/colo-urls/+merge/20860
     jelmer already needs to sign
    status Needs review

https://edge.launchpad.net/1.0/~songofacandy/bzr/fix-523746-dev/+merge/20537
<<<< yay, a member of contributor-agreement-canonical
    status Needs review


The following people need to sign the contributor agreement
Aaron Bentley <https://edge.launchpad.net/1.0/~abentley>
Jelmer Vernooij <https://edge.launchpad.net/1.0/~jelmer>
Martin Pool <https://edge.launchpad.net/1.0/~mbp>
[hydrazine]%