Dear Luca De Luise,
From your log it seems `pycairo` have been installed. First you should check this by starting a Python shell:
/Users/luca/anaconda3/bin/python
Import `pycairo` and check also `igraph` and `pypath` they might be already installed:
import cairo
import igraph
import pypath
If for some reason `python-igraph` could not be installed from the bioconda channel try some other channels, e.g.
conda install -y -c marufr python-igraph
Once it is installed try to import again `pypath`.
Don't hesitate to write if still does not work.
Best wishes,
Denes