Viper does not process integer literals with leading zeros as octal, instead, they're considered decimal. In python mode, they're processed as octal for compatibility. In both cases a suppressable warning is issued. (Just don't do it :-) If you find octal in any python sources, replace it with hex and send Guido a patch.
There's no way to suppress the warning at present.
Examples:
0b11111111 0B11111111 0o777 0O777 0d999 0D999 0xfFf 0xFFf 0777 # OCTAL in python mode: WARNING generated 0777 # DECIMAL in viper mode: WARNING generated