Add missing namespace and XSD to SpotBugs filter file.
diff --git a/src/conf/spotbugs-exclude-filter.xml b/src/conf/spotbugs-exclude-filter.xml
index 7cbba7a..592381b 100644
--- a/src/conf/spotbugs-exclude-filter.xml
+++ b/src/conf/spotbugs-exclude-filter.xml
@@ -21,7 +21,10 @@
false positive nature has been analyzed individually and they have been
put here to instruct findbugs it must ignore them.
-->
-<FindBugsFilter>
+<FindBugsFilter
+ xmlns="https://github.com/spotbugs/filter/3.0.0"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="https://github.com/spotbugs/filter/3.0.0 https://raw.githubusercontent.com/spotbugs/spotbugs/3.1.0/spotbugs/etc/findbugsfilter.xsd">
<!-- TODO Can any of these be done without breaking binary compatibility? -->
<Match>