lumpy_filter returns exit code 84

[rsolano1-uw]

Version of lumpy-sv: Latest v0.3.1

Issue Description: Instead of returning exit code 0, lumpy_filter returns exit code 84

Steps to replicate:

$ lumpy_filter -f /path/to/hs37d5.fa /path/to/347443.merged.matefixed.sorted.markeddups.recal.bam /path/to/347443.split.bam.tmp.bam /path/to/347443.disc.bam.tmp.bam2
[lumpy_filter] extracted splits and discordants from 1077603357 total aligned reads
$ echo $?
84

This is causing runs of smoove to fail because lumpy_filter is exiting with an error code. No other error output is provided by lumpy_filter.