The method GitHubRepository::createPullRequest takes a target repository and the assumption is that a pull request will be created from the repository the method is called on. This is however not the case. The method sets the 'head' parameter to "username:srcbranch", which github will interpret as the source repo being the user's personal fork. However, we need to sometimes create PRs from other forks, e.g. in a different org (openjdk-bots).