Fix an edge case where some databases fail to migrate to 3.0.0 with a unique constraint error.

[sdherr]

See the bug report for more discussion and a stack trace.

Closes #923

[quba42]

Since we are unsure if we really need this, I am converting this to draft (for my sanity). Please think nothing of it.

[quba42]

@sdherr I am 99% sure you needed this because of the way you added migrations to your instance in a different order/state from the pulp_deb main branch. As such, I would like to close this PR in the interest of cleanup. Out of an abundance of caution, I have taken the liberty to push your issue branch into the upstream pulp_deb repository, just in case we do want to recover it later.

Is this acceptable?

[sdherr]

@sdherr I am 99% sure you needed this because of the way you added migrations to your instance in a different order/state from the pulp_deb main branch. As such, I would like to close this PR in the interest of cleanup. Out of an abundance of caution, I have taken the liberty to push your issue branch into the upstream pulp_deb repository, just in case we do want to recover it later.

Is this acceptable?

Yep, sounds good to me, let's close things out.