tasks/lalinference.py: calculate horizon distance with psd.xml.gz to determine...
tasks/lalinference.py: calculate horizon distance with psd.xml.gz to determine the upper limit of distance prior.
Since lalinference_pipe now calculates detectors' horizon distances to determine the distance prior if PSDs are given, psd.xml.gz is downloaded and passed to lalinference_pipe.
cc: @vivien @leo-singer