x11-toolkits/py-gnome2 have pkg-install script called in pre-build target,
checking for existency of py-gnome installation on the system. This script
prevent upgrading of py-gnome2 using portupgrade, in fact, it prevents
building py-gnome2 if any version of py-gnome or py-gnome2 is installed
on the system.
Also the script itself is technically incorrect, because it detects
any version of py-gnome as py-gnome1 because py-gnome2 installs
Fix: Move script execution to pre-install stage.
===> Building for py-gnome-1.99.16_1
py-gnome-1.99.15_1 A set of Python bindings for GNOME 2
py-gnome for GTK+ 1.x was detected.
This packages cannot coexist with py-gnome.
*** Error code 1
Stop in /usr/ports/x11-toolkits/py-gnome2.
I fixed the pkg-instal script. Thanks for reporting.