When deleting remote git branch "error: unable to push to unqualified destination"

The fact that refs/remotes/origin/my_remote_branch exists in your local repository does not imply refs/heads/my_remote_branch exists in the origin remote repository.

Do git fetch -p origin to make refs/remotes/origin/my_remote_branch go away if it's already deleted in origin. The -p option tells fetch to delete any tracking branches that no longer exist in the corresponding remotes; by default they are kept around.

Found question cleaning up old remote git branches and this did the trick

git branch -r -d origin/my_remote_branch

I ran across this when trying to delete a remote branch that had already been deleted. All that was needed was a prune:

git remote prune origin