Excavator: Upgrade dependencies (#157)

###### _excavator_ is a bot for automating changes across repositories.

Changes produced by the versions-props/upgrade-all check.

{runtimeCheckDesc}
To enable or disable this check, please contact the maintainers of Excavator.

versions.props

@@ -18,6 +18,6 @@ junit:junit = 4.12
 org.assertj:assertj-core = 3.12.2
 org.hamcrest:hamcrest-* = 1.3
 org.immutables:value = 2.7.5
-org.jmock:jmock = 2.11.0
+org.jmock:jmock = 2.12.0
 org.mockito:mockito-core = 2.27.0
 ch.qos.logback:logback-classic = 1.1.7