[PATCH stable-2.14] Add error code to OpPrereqError use

['Hrvoje Ribicic' via ganeti-devel]

... otherwise the error is misidentified as an unpacking error.

Signed-off-by: Hrvoje Ribicic <r...@google.com>
---
 lib/cmdlib/instance_storage.py | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/lib/cmdlib/instance_storage.py b/lib/cmdlib/instance_storage.py
index 5fbb593..9b3a998 100644
--- a/lib/cmdlib/instance_storage.py
+++ b/lib/cmdlib/instance_storage.py
@@ -1136,7 +1136,8 @@ def _CheckVgCapacityForNode(node_name, node_info, vg, 
requested):
   lvm_vg_info = utils.storage.LookupSpaceInfoByStorageType(
       space_info, constants.ST_LVM_VG)
   if not lvm_vg_info:
-    raise errors.OpPrereqError("Can't retrieve storage information for LVM")
+    raise errors.OpPrereqError("Can't retrieve storage information for LVM",
+                               errors.ECODE_ENVIRON)
   vg_free = lvm_vg_info.get("storage_free", None)
   if not isinstance(vg_free, int):
     raise errors.OpPrereqError("Can't compute free disk space on node"
-- 
2.5.0.276.gf5e568e