fix(linstor): explicitly notifies a missing res def (#157)

Prior to this change, a `KeyError` was raised that didn't indicate
why a volume info was not found in the event of a missing resource definition.

Signed-off-by: Ronan Abhamon <ronan.abhamon@vates.tech>

Author: Wescoeur

drivers/linstorvolumemanager.py

@@ -960,7 +960,13 @@ def get_volume_info(self, volume_uuid):
         """
 
         volume_name = self.get_volume_name(volume_uuid)
-        return self._get_volumes_info()[volume_name]
+        try:
+            return self._get_volumes_info()[volume_name]
+        except KeyError:
+            raise LinstorVolumeManagerError(
+                f"Could not find info about volume `{volume_uuid}`, the resource definition has likely been deleted",
+                LinstorVolumeManagerError.ERR_VOLUME_NOT_EXISTS
+            )
 
     def get_device_path(self, volume_uuid):
         """