Why would a port use its own existence as an excuse to fail install?

[RW]

On Sat, 15 Feb 2014 22:14:54 -0600
Matthew D. Fuller wrote:


> A nice thing about portmaster is that it's smarter than portupgrade.
> ...
> In this case, I'd guess, portmaster ... Which fails, since it's
> already installed, thus...

For me portupgrade did that upgrade perfectly even though I forgot to
read UPDATING. pkg check reports no errors.