Improve output: distinguish between failed assertions (failures) and unexpected exceptions (errors), and print a filtered stack trace for any exception.

webapp/web/templates/error/error500content.jsp

@@ -0,0 +1,27 @@
+<%-- $This file is distributed under the terms of the license in /doc/license.txt$ --%>
+
+<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
+
+<div class="contents">
+
+<h1>Internal Server Error</h1>
+
+<p class="warning">An internal error has occurred in the server</p>
+
+<p>Please try again later.</p>
+
+<p>If the problem persists, please consider <a href="<c:url value="comments"/>">contacting us</a> and telling us how you arrived here.</p>
+
+<!-- _______________________________Exception__________________________________
+
+500
+Request URI:  ${param.uriStr}
+Exception:    ${param.errStr}
+Stack trace:
+<c:forEach var="trace" items="${pageContext.exception.stackTrace}">
+  ${trace} <%="\n"%>
+</c:forEach>
+___________________________________________________________________________ -->
+
+</div><!-- contents -->
+