storage: do not throw exception if the volume or the pool don't exist

commit 5357b91402fb7a8a73921216926908c08f6ad99d changed the semantic of
conn.get_(vm|pool|interface|nodedev|net), to return None instead of
raising KeyError. Leave the exception handling code in case the
semantic is going to be reverted.

Closes: https://bugzilla.redhat.com/show_bug.cgi?id=1219427

Signed-off-by: Giuseppe Scrivano <gscrivan@redhat.com>

virtManager/delete.py

@@ -236,7 +236,11 @@ def populate_storage_list(storage_list, vm, conn):
         if disk.source_pool:
             try:
                 pool = conn.get_pool(disk.source_pool)
+                if pool is None:
+                    return disk.path
                 vol = pool.get_volume(disk.path)
+                if vol is None:
+                    return disk.path
                 return vol.get_target_path()
             except KeyError:
                 return disk.path

virtManager/details.py

@@ -2700,12 +2700,14 @@ class vmmDetails(vmmGObjectUI):
         if not path:
             size = "-"
         else:
+            vol = None
             if source_pool:
                 try:
                     pool = self.conn.get_pool(source_pool)
-                    vol = pool.get_volume(path)
+                    if pool is not None:
+                        vol = pool.get_volume(path)
                 except KeyError:
-                    vol = None
+                    pass
             else:
                 vol = self.conn.get_vol_by_path(path)