python-libnacl-1.4.4-34.7.x86_64.rpm for SLE 12 SP3 depends on libsodium23-1.0.16 RPM, which contains libsodium.so.23.1.0 symlinked as libsodium.so.23 but not as libsodium.so. But python-libnacl code only looks for libsodium.so and libsodium.so.18 and below.

If this version of python-libnacl cannot use libsodium.so.23, the RPM dependency should be changed; if it can (as it looks like after minimal testing), then the code in /usr/lib/python2.7/site-packages/libnacl/init.py should be modified to also look for libsodium.so.23. Adding 23 to the __SONAMES array on line 12 should be the simplest fix.

Filed the issue upstream: https://github.com/saltstack/libnacl/issues/111

@fimatkurk, the libnacl 1.6.1 has support for libsodium 23 libnacl 1.4.4 is a very old version.