I was able to reproduce the error. Anaconda uses by default python3.6. For some reason compiling orthpol_light against the libgfortran provided by anaconda raises that undefined symbol error.
A workaround is to use python3.5 (which is the version supported by Ubuntu16.04). To do so you can create a new environment in conda (which is anyway advised in order to keep things tided):
$ conda create -n tm python=3.5 numpy scipy
then activate the newly created environment
$ source activate tm
and installing orthpol_light through pip
$ pip install orthpol_light
I will dig into figuring out whether the problem with python3.6 is only related to anaconda or more general.