[Internal] Throw error if no notebook author (#2960)

# Description

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Signed-off-by: Brynn Yin <[email protected]>

scripts/docs/doc_generation.ps1

@@ -142,16 +142,15 @@ function Add-Metadata{
     )
     if (-not $AuthorList){
         # Skip insert if author list not set
-        Write-Host "Skip Add Metadata: $NotebookPath - Author list not set"
+        throw "Skip Add Metadata: $NotebookPath - Author list not set"
         return
     }
     $NotebookContent = Get-Content $NotebookPath -Raw | ConvertFrom-Json
     # Covert to System.Collections.ArrayList to avoid 'Collection was of a fixed size' error.
     $NotebookContent.cells = [System.Collections.ArrayList]::new($NotebookContent.cells)
     if($NotebookContent.cells[0].source.Length -gt 1){
         # If the first cell length > 1, indicate there are more things than title it self in the first cell
-        Write-Host "Skip Add Metadata: $NotebookPath - First cell length > 1, only leave title to that cell."
-        Write-Host "$(NotebookContent.cells[0].source)"
+        throw "Skip Add Metadata: $NotebookPath - First cell length > 1, only leave title to that cell. $(NotebookContent.cells[0].source)"
         return
     }
     $MetadataFormat = "Authored by: {0}{1}"