Adapt to Gerrit 2.14 and Java 8

Change-Id: I3539e836cf96f974626c33fb28f6b59f136909af

src/main/java/com/googlesource/gerrit/plugins/scripting/groovyprovider/GroovyPluginScanner.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/scripting/groovyprovider/GroovyPluginScanner.java b/src/main/java/com/googlesource/gerrit/plugins/scripting/groovyprovider/GroovyPluginScanner.java
index 77bfcfd..8718e39 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/scripting/groovyprovider/GroovyPluginScanner.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/scripting/groovyprovider/GroovyPluginScanner.java
@@ -13,7 +13,7 @@
 // limitations under the License.
 package com.googlesource.gerrit.plugins.scripting.groovyprovider;
 
-import com.google.common.base.Optional;
+import java.util.Optional;
 import com.google.common.collect.Sets;
 import com.google.gerrit.server.plugins.AbstractPreloadedPluginScanner;
 import com.google.gerrit.server.plugins.InvalidPluginException;
@@ -54,7 +54,7 @@
 
   @Override
   public Optional<PluginEntry> getEntry(String resourcePath) {
-    return Optional.absent();
+    return Optional.empty();
   }
 
   @Override