OK, now that I've moved from a phone to a workstation, let me elaborate:
- bzip2's last upgrade was at 4.7-release: it was upgraded to 1.0.6.
- There was a revision of the port for 4.9-release, but it did not alter the binary executables in the package. USE_GROFF=YES was added to the port's Makefile.
- It appears that pkg_add is attempting to install bzip2, which is a run-time dependency for python. Your console output may not be complete; pkg_add produces output which will overlay existing text.
- It appears that bzip2 is already installed, although with different checksums.
There are several possible reasons for the collision and checksum errors.
The most likely cause is an incorrect $PKG_PATH -- either pointing to the wrong architecture (e.g.: i386 instead of amd64, or vice versa) or trying to use snapshot packages while running a -release.
Another cause could be a damaged or out-of-sync installed-package database -- pkg_add and pkg_delete manage this data base in file structures located in /var/db/pkg. Issuing
$ pkginfo | grep bzip2 will show you if the database recognizes bzip2 as already installed or not. And then you can test any of the individually listed files with pkg_info -E to check the file against the database to determine which package installed it, such as
$ pkg_info -E /usr/local/bin/bzip2
If your $PKG_PATH is confirmed to be correct, and bzip2 appears to be installed properly, there may have been a package signature change between -release packages for bzip; a simple
# pkg_add -r bzip2 might solve the problem.