Python 2.7.12 and openjdk may be the problems.
I also had same problem, but after installing Python Anaconda 2 it works.
Install and use Oracle Java rather than openJDK. Oracle Java is recommended for SeaDAS7.4 installation.
Eko
seadas 7.4, update_luts.py
seadas 7.4, update_luts.py
In case other fedora users find this thread -- I agree that the OCSSW scripts should "just work" with fedora 26 python2.7, but they don't, hence RH Bugzilla no. 1500775.