Update to Mockito 2.7.12

fix gh-933

Author: kazuki43zoo

pom.xml

@@ -222,7 +222,7 @@
     <dependency>
       <groupId>org.mockito</groupId>
       <artifactId>mockito-core</artifactId>
-      <version>2.4.2</version>
+      <version>2.7.12</version>
       <scope>test</scope>
     </dependency>
     <!-- Do not go to 2.x until we are on jdk7 -->