don't print stacktrace when assert fails

commons/src/main/java/lcsb/mapviewer/common/UnitTestFailedWatcher.java

@@ -6,6 +6,8 @@ import org.junit.runner.Description;
 public class UnitTestFailedWatcher extends TestWatcher {
   @Override
   protected void failed(Throwable e, Description description) {
-    e.printStackTrace();
+    if (!(e instanceof AssertionError)) {
+      e.printStackTrace();
+    }
   }
 }