Fix cn_metrics.py not to fail on empty yaml input (#342)

* Fix cn_metrics.py not to fail if there are no nodes in the yaml output.

Signed-off-by: Greg Becker <[email protected]>

* Fix list item test.

Signed-off-by: Greg Becker <[email protected]>

Author: beckerg

tools/scripts/cn_metrics.py

@@ -12,7 +12,12 @@
 import json
 import pathlib
 import signal
-from typing import Any, Dict, OrderedDict, Optional
+from typing import Any, Optional
+
+try:
+    from typing import OrderedDict
+except ImportError:
+    from typing import Dict as OrderedDict
 
 desc = (
     "print cn tree shape\n\n"
@@ -69,6 +74,9 @@ def full_tree(ybuf: Optional[OrderedDict[str, Any]], opt):
     if ybuf["info"]["open"] == False:
         return
 
+    if not ybuf.get("nodes", []):
+        return
+
     # Print info for each node in the kvs.
     #
     for node in ybuf["nodes"]: