Thanks for the speedy reply @jon! When attempting to push my branch, with the one commit in it, I get the following response:
git -c diff.mnemonicprefix=false -c core.quotepath=false -c credential.helper=sourcetree push -v --set-upstream origin fix-ReadmeUrl-djspaceg:fix-ReadmeUrl-djspaceg
Pushing to https://github.com/tessel/ir-attx4.git
remote: Permission to tessel/ir-attx4.git denied to djspaceg.
fatal: unable to access 'https://github.com/tessel/ir-attx4.git/': The requested URL returned error: 403
Completed with errors, see above
Technically I never got to the PR phase, since the pushing-the-branch phase never completed.