For a url like say file:///cvmfs/singularity.opensciencegrid.org/pycbc/pycbc-el7:latest pegasus tries to compute the suffix from incorrect part.

Invalid suffix .opensciencegrid.org/pycbc/pycbc-el7:latest determined singularity image url url -> file:///cvmfs/singularity.opensciencegrid.org/pycbc/pycbc-el7:latest , protocol -> file , host -> , path -> /cvmfs/singularity.opensciencegrid.org/pycbc/pycbc-el7:latest , url-prefix -> file:// at edu.isi.pegasus.planner.catalog.transformation.classes.Container.computeLFN(Container.java:192)

it should be only from pycbc-el7:latest