fix: error if user tries to use --py with cpp artifact

Author: gforsyth

tools/rapids-artifact-name

@@ -104,8 +104,8 @@ if (( pure_flag == 1 && py_flag == 1 )); then
   exit 1
 fi
 
-if [[ "${pkg_lang}" == "cpp" ]] && (( stable_flag == 1 || pure_flag == 1 )); then
-  rapids-echo-stderr "'--stable' and '--pure' are only valid for Python package types"
+if [[ "${pkg_lang}" == "cpp" ]] && (( stable_flag == 1 || pure_flag == 1 || py_flag == 1)); then
+  rapids-echo-stderr "'--stable', '--py', and '--pure' are only valid for Python package types"
   exit 1
 fi