How to use the dugite.GitError.BranchAlreadyExists function in dugite

return 'A submodule was removed from .gitmodules, but the folder still exists in the repository. Delete the folder, commit the change, then try again.'
    case DugiteError.SubmoduleRepositoryDoesNotExist:
      return 'A submodule points to a location which does not exist.'
    case DugiteError.InvalidSubmoduleSHA:
      return 'A submodule points to a commit which does not exist.'
    case DugiteError.LocalPermissionDenied:
      return 'Permission denied.'
    case DugiteError.InvalidMerge:
      return 'This is not something we can merge.'
    case DugiteError.InvalidRebase:
      return 'This is not something we can rebase.'
    case DugiteError.NonFastForwardMergeIntoEmptyHead:
      return 'The merge you attempted is not a fast-forward, so it cannot be performed on an empty branch.'
    case DugiteError.PatchDoesNotApply:
      return 'The requested changes conflict with one or more files in the repository.'
    case DugiteError.BranchAlreadyExists:
      return 'A branch with that name already exists.'
    case DugiteError.BadRevision:
      return 'Bad revision.'
    case DugiteError.NotAGitRepository:
      return 'This is not a git repository.'
    case DugiteError.ProtectedBranchForcePush:
      return 'This branch is protected from force-push operations.'
    case DugiteError.ProtectedBranchRequiresReview:
      return 'This branch is protected and any changes requires an approved review. Open a pull request with changes targeting this branch instead.'
    case DugiteError.PushWithFileSizeExceedingLimit:
      return "The push operation includes a file which exceeds GitHub's file size restriction of 100MB. Please remove the file from history and try again."
    case DugiteError.HexBranchNameRejected:
      return 'The branch name cannot be a 40-character string of hexadecimal characters, as this is the format that Git uses for representing objects.'
    case DugiteError.ForcePushRejected:
      return 'The force push has been rejected for the current branch.'
    case DugiteError.InvalidRefLength: