message: Use consistent import prefix for bigtable
diff: @@ -258,7 +258,7 @@ class GameQueue:
  r = rows.pop()
  r.delete()
  batch.append(r)
  - if len(batch) >= google.cloud.bigtable.row.MAX_MUTATIONS:
  + if len(batch) >= bigtable.row.MAX_MUTATIONS:
  mutate_batch()
  mutate_batch()
  