Merge branch '172-modbuild-read-from-stdin-if-no-variants-files-are-found' into 'Pmodules-1.0'

Resolve "modbuild read from stdin if no variants files are found"

See merge request Pmodules/src!145

Pmodules/modbuild.in

@@ -297,6 +297,9 @@ find_variants_files(){
                         || [[ -e "${f}.$(uname -s)" ]] \
                         || files+=( "$f" )
 	done
+	if (( ${#files[@]} == 0 )); then
+		std::die 2 "No suitable variants file found!"
+	fi
         (( nullglob_set == 1 )) && shopt -u nullglob
 	std::upvar "$1" "${files[@]}"
 }