Use logger built-in format

Change-Id: I593514b2f3ab75bc58e8edcec5f3981de4c4c82a
diff --git a/src/main/java/com/ericsson/gerrit/plugins/projectgroupstructure/DefaultAccessRights.java b/src/main/java/com/ericsson/gerrit/plugins/projectgroupstructure/DefaultAccessRights.java
index 466fb55..a4b56c1 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/projectgroupstructure/DefaultAccessRights.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/projectgroupstructure/DefaultAccessRights.java
@@ -146,7 +146,7 @@
     try {
       RefPattern.validateRegExp(refPattern);
     } catch (InvalidNameException e) {
-      log.error("Invalid ref name: " + e.getMessage());
+      log.error("Invalid ref name: {}", e.getMessage());
       return false;
     }
     return true;
diff --git a/src/main/java/com/ericsson/gerrit/plugins/projectgroupstructure/ProjectCreationValidator.java b/src/main/java/com/ericsson/gerrit/plugins/projectgroupstructure/ProjectCreationValidator.java
index e422f17..278987c 100644
--- a/src/main/java/com/ericsson/gerrit/plugins/projectgroupstructure/ProjectCreationValidator.java
+++ b/src/main/java/com/ericsson/gerrit/plugins/projectgroupstructure/ProjectCreationValidator.java
@@ -139,10 +139,9 @@
           .getBoolean(DISABLE_GRANTING_PROJECT_OWNERSHIP, false);
     } catch (NoSuchProjectException e) {
       log.error(
-          "Failed to check project config for "
-              + parentCtrl.getProject().getName()
-              + ": "
-              + e.getMessage(),
+          "Failed to check project config for {}: {}",
+          parentCtrl.getProject().getName(),
+          e.getMessage(),
           e);
       throw new ValidationException(AN_ERROR_OCCURRED_MSG);
     }
@@ -173,7 +172,7 @@
       }
       return AccountGroup.UUID.parse(groupInfo.id);
     } catch (RestApiException | OrmException | IOException e) {
-      log.error("Failed to create project " + name + ": " + e.getMessage(), e);
+      log.error("Failed to create project {}: {}", name, e.getMessage(), e);
       throw new ValidationException(AN_ERROR_OCCURRED_MSG);
     }
   }