psu: Split out the key logic to allow for its local storage

Summary:
Allow for the default key to be provided by a python module
(but still allow the user to override it). This allows for
the local storage of the BMC to be modified to allow for
persistent store of it.

Test Plan: TODO

Reviewed By: ifel

Differential Revision: D82985056

fbshipit-source-id: ba236c3cf84bb808898519b5c4c91adc0c554dbe

Author: amithash

common/recipes-core/psu-update/files/delta_key.py

@@ -0,0 +1 @@
+key = None

common/recipes-core/psu-update/files/psu-update-delta-orv3.py

@@ -22,9 +22,10 @@
 )
 from pyrmd import ModbusException, RackmonInterface as rmd
 
+import delta_key
 
 parser = get_parser()
-parser.add_argument("--key", type=auto_int, required=True, help="Sec key")
+parser.add_argument("--key", type=auto_int, default=delta_key.key, help="Sec key")
 
 
 class StatusRegister:
@@ -293,6 +294,9 @@ def print_revision(addr):
 
 def main():
     args = parser.parse_args()
+    if args.key is None:
+        print("PSU Update Key is needed to upgrade this device")
+        sys.exit(1)
     with suppress_monitoring(args.addr):
         try:
             print_revision(args.addr)