Log: Print stack trace on exception

Change-Id: I45b0886fe25da73c09aff4f4910f6826081ae4f7

src/main/java/com/googlesource/gerrit/plugins/importer/ImportLog.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/importer/ImportLog.java b/src/main/java/com/googlesource/gerrit/plugins/importer/ImportLog.java
index 38e0f8b..8c6f27e 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/importer/ImportLog.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/importer/ImportLog.java
@@ -14,6 +14,7 @@
 
 package com.googlesource.gerrit.plugins.importer;
 
+import com.google.common.base.Throwables;
 import com.google.common.collect.HashMultimap;
 import com.google.common.collect.Multimap;
 import com.google.gerrit.audit.AuditEvent;
@@ -96,7 +97,7 @@
     event.setProperty(TARGET_PROJECT_NAME, targetProject.get());
 
     if (ex != null) {
-      event.setProperty(ERROR, ex.toString());
+      event.setProperty(ERROR, Throwables.getStackTraceAsString(ex));
     }
 
     log.callAppenders(event);