lang/python - wrong usage of PORTUPGRADE variable

[Alexander Botero-Lowry]

> I expect, that upgrade of site packages should work with default options 
> mentioned above (backup & make tbz packages in directory defined by env 
> variable PACKAGES, or any other options from PORTUPGRADE env variable)
> 
> Please CC me, I am not subscribed.
I just committed a fix to use PORTUPGRADE_CMD and PKG_WHICH_CMD instead.

alex