add error message to the google drive document loader (#2186)

When downloading a google doc, if the document is not a google doc type,
for example if you uploaded a .DOCX file to your google drive, the error
you get is not informative at all. I added a error handler which print
the exact error occurred during downloading the document from google
docs.

langchain/document_loaders/googledrive.py

@@ -142,6 +142,7 @@ class GoogleDriveLoader(BaseLoader, BaseModel):
         from io import BytesIO
 
         from googleapiclient.discovery import build
+        from googleapiclient.errors import HttpError
         from googleapiclient.http import MediaIoBaseDownload
 
         creds = self._load_credentials()
@@ -151,8 +152,16 @@ class GoogleDriveLoader(BaseLoader, BaseModel):
         fh = BytesIO()
         downloader = MediaIoBaseDownload(fh, request)
         done = False
+        try:
             while done is False:
                 status, done = downloader.next_chunk()
+
+        except HttpError as e:
+            if e.resp.status == 404:
+                print("File not found: {}".format(id))
+            else:
+                print("An error occurred: {}".format(e))
+
         text = fh.getvalue().decode("utf-8")
         metadata = {"source": f"https://docs.google.com/document/d/{id}/edit"}
         return Document(page_content=text, metadata=metadata)