Make _poll_for_status more user-friendly

NOTE: _poll_for_status is a private method, which is used only in shell
      module, so we can modify it without backward compatibility.

_poll_for_status is used for various resources with different interfaces.

In case of snapshotting, it works with Image resources, which doesn't have
"fault" attribute in "error" state. To prevent AttributeError, we should take
this into account.

Also, an exception raised by _poll_for_status(InstanceInErrorState) should
not be hardcoded for one type of resource, so this exception is renamed to
ResourceInErrorState. An exception InstanceInDeletedState, which is also
can be raised by _poll_for_status, is not modified, since I don't know cases
when it can be used with resources other than Server.

Change-Id: Ie0ee96999376cbf608caa1cf8521dbef5c939b52
Closes-Bug: #1538073

1 files changed, 9 insertions, 3 deletions

diff --git a/novaclient/exceptions.py b/novaclient/exceptions.py
index 94591f26..b9bdf114 100644
--- a/novaclient/exceptions.py
+++ b/novaclient/exceptions.py
@@ -77,9 +77,15 @@ class ConnectionRefused(Exception):
         return "ConnectionRefused: %s" % repr(self.response)
 
 
-class InstanceInErrorState(Exception):
-    """Instance is in the error state."""
-    pass
+class ResourceInErrorState(Exception):
+    """Resource is in the error state."""
+
+    def __init__(self, obj):
+        msg = "`%s` resource is in the error state" % obj.__class__.__name__
+        fault_msg = getattr(obj, "fault", {}).get("message")
+        if fault_msg:
+            msg += "due to '%s'" % fault_msg
+        self.message = "%s." % msg
 
 
 class VersionNotFoundForAPIMethod(Exception):