The complete error actually is:

Cannot find required executable /usr/bin/7za
pkgadd: ERROR: class action script din not complete successfully

That was the error message displaced when I tried installing two Sun packages as requested by a user, SUNWeu8os and SUNWeulof.

Packages can be found in tge Solaris 10 disk release 5/08. When i tried installing the package I got the error above.

There are two ways you can get that binary and one of them is by using the installation disk of Solaris 10 5/08.

Another one is by installing patch 137321-01 for sparc and 137322-01 for x86