Add slf4j-nop dependency.

Author: uhafner

pom.xml

@@ -21,6 +21,7 @@
     <java.level>8</java.level>
     <jenkins-test-harness.version>2.49</jenkins-test-harness.version>
     <spotbugs.failOnError>false</spotbugs.failOnError>
+    <slf4j-nop.version>1.7.26</slf4j-nop.version>
 
     <!-- Library Dependencies Versions -->
     <error-prone.version>2.3.3</error-prone.version>
@@ -107,6 +108,11 @@
   <dependencies>
 
     <!-- Project Dependencies -->
+    <dependency>
+      <groupId>org.slf4j</groupId>
+      <artifactId>slf4j-nop</artifactId>
+      <version>${slf4j-nop.version}</version>
+    </dependency>
     <dependency>
       <groupId>com.github.spotbugs</groupId>
       <artifactId>spotbugs-annotations</artifactId>