Change use of deprecated OIIO argparse::error_message to newer geterror
Change use of deprecated OIIO argparse::error_message to newer geterror

fpsunflower/OpenShadingLanguage,sjparker/OpenShadingLanguage,rlmh/OpenShadingLanguage,lgritz/OpenShadingLanguage,aconty/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,aconty/OpenShadingLanguage,mcanthony/OpenShadingLanguage,brechtvl/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,imageworks/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,rlmh/OpenShadingLanguage,sjparker/OpenShadingLanguage,gzorin/OpenShadingLanguage,mcanthony/OpenShadingLanguage,mcanthony/OpenShadingLanguage,lgritz/OpenShadingLanguage,svenstaro/OpenShadingLanguage,juvenal/OpenShadingLanguage,sjparker/OpenShadingLanguage,aconty/OpenShadingLanguage,aconty/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,Anteru/OpenShadingLanguage,Anteru/OpenShadingLanguage,svenstaro/OpenShadingLanguage,brechtvl/OpenShadingLanguage,imageworks/OpenShadingLanguage,lgritz/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,mcanthony/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,gzorin/OpenShadingLanguage,rlmh/OpenShadingLanguage,brechtvl/OpenShadingLanguage,brechtvl/OpenShadingLanguage,aconty/OpenShadingLanguage,Anteru/OpenShadingLanguage,Anteru/OpenShadingLanguage,juvenal/OpenShadingLanguage,fpsunflower/OpenShadingLanguage,imageworks/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,imageworks/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,juvenal/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,gzorin/OpenShadingLanguage,lgritz/OpenShadingLanguage,brechtvl/OpenShadingLanguage,sjparker/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage,svenstaro/OpenShadingLanguage,rlmh/OpenShadingLanguage,juvenal/OpenShadingLanguage,amartinez-cg/OpenShadingLanguage,imageworks/OpenShadingLanguage,svenstaro/OpenShadingLanguage,gzorin/OpenShadingLanguage,gzorin/OpenShadingLanguage,johnhaddon/OpenShadingLanguage,lgritz/OpenShadingLanguage,yaroslav-tarasov/OpenShadingLanguage