ci: Improve error handling for Python backend model initialization failures

qa/L0_backend_python/test.sh

@@ -407,6 +407,44 @@ and shared memory pages after starting triton equals to $current_num_pages \n***
     exit 1
 fi
 
+
+# Test model with non-existent model file
+# The model.py file is intentionally not created to trigger the failure.
+rm -fr ./models
+mkdir -p models/non_existent_model/1
+cp ../python_models/identity_fp32/config.pbtxt ./models/non_existent_model/config.pbtxt
+(cd models/non_existent_model && \
+          sed -i "s/^name:.*/name: \"non_existent_model\"/" config.pbtxt)
+
+SERVER_LOG="./non_existent_model_server.log"
+CLIENT_LOG="./non_existent_model_client.log"
+ERROR_MESSAGE_1="Failed to preinitialize Python stub: Python model file not found in '`pwd`/models/non_existent_model/1/model.py'"
+ERROR_MESSAGE_2="failed to load 'non_existent_model'"
+
+prev_num_pages=`get_shm_pages`
+run_server
+if [ "$SERVER_PID" != "0" ]; then
+    echo -e "*** FAILED: unexpected success starting $SERVER" >> $CLIENT_LOG
+    RET=1
+    kill_server
+else
+    if grep -q "$ERROR_MESSAGE_1" $SERVER_LOG; then
+        echo -e "Found \"$ERROR_MESSAGE_1\"" >> $CLIENT_LOG
+    else
+        echo -e "Not found \"$ERROR_MESSAGE_1\" in $SERVER_LOG" >> $CLIENT_LOG
+        cat $SERVER_LOG >> $CLIENT_LOG
+        RET=1
+    fi
+
+    if grep -q "$ERROR_MESSAGE_2" $SERVER_LOG; then
+        echo -e "Found \"$ERROR_MESSAGE_2\"" >> $CLIENT_LOG
+    else
+        echo -e "Not found \"$ERROR_MESSAGE_2\" in $SERVER_LOG" >> $CLIENT_LOG
+        cat $SERVER_LOG >> $CLIENT_LOG
+        RET=1
+    fi
+fi
+
 # Disable env test for Jetson since cloud storage repos are not supported
 # Disable ensemble, io and bls tests for Jetson since GPU Tensors are not supported
 # Disable variants test for Jetson since already built without GPU Tensor support