autopkg over-rides failure

gistfile1.txt

autopkg hefike$ Code/autopkg make-override Firefox.munki
Traceback (most recent call last):
  File "Code/autopkg", line 1017, in <module>
    sys.exit(main(sys.argv))
  File "Code/autopkg", line 1011, in main
    exit(subcommands[verb]['function'](argv))
  File "Code/autopkg", line 723, in make_override
    FoundationPlist.writePlist(override_plist, override_out_file)
  File "/Users/hefike/Desktop/dev/autopkg/Code/FoundationPlist/FoundationPlist.py", line 103, in writePlist
    "Failed to write plist data to %s" % filepath)
FoundationPlist.FoundationPlist.NSPropertyListWriteException: Failed to write plist data to /Users/hefike/Library/AutoPkg/RecipeOverrides/Firefox.munki.recipe