PEP8 fixes on convert_precision.py
PEP8 fixes on convert_precision.py

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