overall better handling and usage of exceptions

items/zfs_dataset.py

@@ -1,5 +1,6 @@
 from pipes import quote
 
+from bundlewrap.exceptions import BundleError
 from bundlewrap.items import Item
 from bundlewrap.utils.text import mark_for_translation as _
 
@@ -120,7 +121,7 @@ class ZFSDataset(Item):
                 yield item.id
 
         if not pool_item_found:
-            raise Exception(_(
+            raise BundleError(_(
                 "ZFS dataset {dataset} resides on pool {pool} but item "
                 "{dep} does not exist"
             ).format(