fix: Include traceback in Java Exceptions caused by Python Exceptions

StringWriter should be used instead of ByteArrayOutputStream to capture
output.

python/jpyinterpreter/src/main/java/ai/timefold/jpyinterpreter/util/TracebackUtils.java

@@ -1,17 +1,17 @@
 package ai.timefold.jpyinterpreter.util;
 
-import java.io.ByteArrayOutputStream;
 import java.io.PrintWriter;
+import java.io.StringWriter;
 
 public class TracebackUtils {
     private TracebackUtils() {
 
     }
 
     public static String getTraceback(Throwable t) {
-        ByteArrayOutputStream byteOutputStream = new ByteArrayOutputStream();
-        PrintWriter printWriter = new PrintWriter(byteOutputStream);
+        var output = new StringWriter();
+        PrintWriter printWriter = new PrintWriter(output);
         t.printStackTrace(printWriter);
-        return byteOutputStream.toString();
+        return output.toString();
     }
 }

python/jpyinterpreter/src/test/java/ai/timefold/jpyinterpreter/util/TracebackUtilsTest.java

@@ -0,0 +1,18 @@
+package ai.timefold.jpyinterpreter.util;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+public class TracebackUtilsTest {
+    @Test
+    public void getTraceback() {
+        try {
+            throw new RuntimeException("A runtime error has occurred.");
+        } catch (RuntimeException e) {
+            assertThat(TracebackUtils.getTraceback(e))
+                    .contains("A runtime error has occurred.")
+                    .contains(TracebackUtilsTest.class.getCanonicalName());
+        }
+    }
+}