After publishing a Geoprocessing Service from a .pyt, ArcGIS for Server's generated .pyt does not append ‘arcpy.env.packageWorkspace’ to the ‘g_ESRI_variable’ path when using a UNC share or mapped network drive location at version 10.3.1.
Works at 10.4.
If the directory is not referenced in the datastore, it properly gets copied and the path looks like: g_ESRI_variable_1 = os.path.join(arcpy.env.packageWorkspace,u'..\\cd\\styles\\ESRI.ServerStyle')
If the directory is referenced in the datastore, the file is not copied.