Merge branch 'stable-2.16' into stable-3.0

* stable-2.16:
  Make toString(), hashCode(), equals() and friends final in AutoValue classes
  Schema_169: Increase log severity level
  Schema_146: Fix FutureReturnValueIgnored warning flagged by error prone
  Fix various usages of the Flogger API
  Schema_169: Fix usage of Flogger to log exception stack trace
  Keep alive database connection to prevent exceeding wait timeout

Change-Id: Ic8885a66acb123b52a30a74a63a2b2e5411dd453

java/com/google/gerrit/server/config/ConfigKey.java

@@ -34,7 +34,7 @@ public abstract class ConfigKey {
   }
 
   @Override
-  public String toString() {
+  public final String toString() {
     StringBuilder sb = new StringBuilder();
     sb.append(section()).append(".");
     if (subsection() != null) {

java/com/google/gerrit/server/config/PluginConfigFactory.java

@@ -230,7 +230,8 @@ public class PluginConfigFactory implements ReloadPluginListener {
       cfg.load();
     } catch (ConfigInvalidException e) {
       // This is an error in user input, don't spam logs with a stack trace.
-      logger.atWarning().log("Failed to load %s: %s", pluginConfigFile.toAbsolutePath(), e);
+      logger.atWarning().log(
+          "Failed to load %s: %s", pluginConfigFile.toAbsolutePath(), e.getMessage());
     } catch (IOException e) {
       logger.atWarning().withCause(e).log("Failed to load %s", pluginConfigFile.toAbsolutePath());
     }

java/com/google/gerrit/server/config/ScheduleConfig.java

@@ -194,7 +194,7 @@ public abstract class ScheduleConfig {
   }
 
   @Override
-  public String toString() {
+  public final String toString() {
     StringBuilder b = new StringBuilder();
     b.append(formatValue(keyInterval()));
     b.append(", ");