don't drop the underlying cause when thing can't be read

git-svn-id: https://svn.apache.org/repos/asf/ant/core/trunk@531427 13f79535-47bb-0310-9956-ffa450edef68

src/main/org/apache/tools/ant/types/FilterSet.java

@@ -370,7 +370,7 @@ public class FilterSet extends DataType implements Cloneable {
               }
            } catch (Exception ex) {
               throw new BuildException("Could not read filters from file: "
-                  + filtersFile);
+                  + filtersFile,ex);
            } finally {
               FileUtils.close(in);
            }