hilary-greavess-macbook:guix_bug hgreaves$ therion guix_bug.thconfig 
therion 5.2
sh: cavern: command not found
initialization file: /etc/therion.ini
reading ... done
configuration file: guix_bug.thconfig
reading ... done
reading source files ... done
preprocessing database ... done
scanning centreline tree ... done
searching for centerline loops ... done
calculating station coordinates ... done
calculating basic statistics ... done
processing extended elevation ... done
processing references ... Bus error
