Declare IOException thrown by #createEmulatorConfiguration

Change-Id: I9fdb4740dab81cf84f871202f9a7999e0a50f0e2

src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerEmulatorContainer.java

diff --git a/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerEmulatorContainer.java b/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerEmulatorContainer.java
index 203da39..fc11e73 100644
--- a/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerEmulatorContainer.java
+++ b/src/test/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerEmulatorContainer.java
@@ -34,6 +34,8 @@
 import com.google.cloud.spanner.SpannerOptions;
 import com.google.gerrit.server.config.PluginConfigFactory;
 import com.google.inject.Inject;
+
+import java.io.IOException;
 import java.util.Collections;
 import java.util.concurrent.ExecutionException;
 import org.eclipse.jgit.lib.Config;
@@ -154,7 +156,7 @@
     return createDatabaseClient(pluginConfig);
   }
 
-  private Configuration createEmulatorConfiguration() {
+  private Configuration createEmulatorConfiguration() throws IOException {
     Config refDbConfig = new Config();
     refDbConfig.setBoolean(Configuration.SECTION, null, "useEmulator", true);
     refDbConfig.setString(SECTION, SUBSECTION, INSTANCE_KEY, SPANNER_INSTANCE_ID);