Change source_separate to separate in test_source_file.py.
Change source_separate to separate in test_source_file.py.

shenqicang/openmc,smharper/openmc,samuelshaner/openmc,amandalund/openmc,smharper/openmc,smharper/openmc,nhorelik/openmc,walshjon/openmc,lilulu/openmc,wbinventor/openmc,paulromano/openmc,mit-crpg/openmc,samuelshaner/openmc,liangjg/openmc,wbinventor/openmc,amandalund/openmc,mjlong/openmc,johnnyliu27/openmc,paulromano/openmc,paulromano/openmc,kellyrowland/openmc,liangjg/openmc,shikhar413/openmc,kellyrowland/openmc,wbinventor/openmc,walshjon/openmc,johnnyliu27/openmc,walshjon/openmc,johnnyliu27/openmc,walshjon/openmc,mjlong/openmc,sxds/opemmc,smharper/openmc,bhermanmit/openmc,samuelshaner/openmc,wbinventor/openmc,samuelshaner/openmc,liangjg/openmc,bhermanmit/openmc,liangjg/openmc,mit-crpg/openmc,amandalund/openmc,shenqicang/openmc,shikhar413/openmc,lilulu/openmc,shikhar413/openmc,paulromano/openmc,shikhar413/openmc,johnnyliu27/openmc,sxds/opemmc,mit-crpg/openmc,nhorelik/openmc,amandalund/openmc,lilulu/openmc,mit-crpg/openmc