Declare BuildException in Sleep.validate explicitly.

Submitted by:	Steve Loughran <steve_l@iseran.com>


git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@269226 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/taskdefs/Sleep.java

@@ -177,7 +177,8 @@ public class Sleep extends Task {
      *
      * @throws BuildException if something is invalid
      */
-    public void validate() {
+    public void validate() 
+        throws BuildException {
         long sleepTime = getSleepTime();
         if (getSleepTime() < 0) {
             throw new BuildException("Negative sleep periods are not supported");