Firstly, in time honored tradition - the maven enforcer plugin crashes with a null pointer exception, compatibility hasn't been maintained by the Apache team in their latest product iteration. As far as I can see, the sole purpose of this plugin is to enforce the use of Maven 3.0 during builds - Maven 3.0 is obsolete btw.

⚛︎□▷ mvn compile
[INFO] Scanning for projects...
[WARNING] The project com.basho.riak:riak-client:jar:2.1.2-SNAPSHOT uses prerequisites which is only intended for maven-plugin projects but not for non maven-plugin projects. For such purposes you should use the maven-enforcer-plugin. See https://maven.apache.org/enforcer/enforcer-rules/requireMavenVersion.html
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] Building Riak Client for Java 2.1.2-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[INFO]
[INFO] --- maven-enforcer-plugin:1.4.1:enforce (enforce-property) @ riak-client ---
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.751 s
[INFO] Finished at: 2018-02-26T14:16:28Z
[INFO] Final Memory: 9M/32M
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-enforcer-plugin:1.4.1:enforce (enforce-property) on project riak-client: Execution enforce-property of goal org.apache.maven.plugins:maven-enforcer-plugin:1.4.1:enforce failed: An API incompatibility was encountered while executing org.apache.maven.plugins:maven-enforcer-plugin:1.4.1:enforce: java.lang.ExceptionInInitializerError: null
[ERROR] -----------------------------------------------------
[ERROR] realm =    plugin>org.apache.maven.plugins:maven-enforcer-plugin:1.4.1
[ERROR] strategy = org.codehaus.plexus.classworlds.strategy.SelfFirstStrategy
[ERROR] urls[0] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/plugins/maven-enforcer-plugin/1.4.1/maven-enforcer-plugin-1.4.1.jar
[ERROR] urls[1] = file:/Users/bryanhunt/.m2/repository/backport-util-concurrent/backport-util-concurrent/3.1/backport-util-concurrent-3.1.jar
[ERROR] urls[2] = file:/Users/bryanhunt/.m2/repository/org/codehaus/plexus/plexus-interpolation/1.11/plexus-interpolation-1.11.jar
[ERROR] urls[3] = file:/Users/bryanhunt/.m2/repository/org/slf4j/slf4j-jdk14/1.5.6/slf4j-jdk14-1.5.6.jar
[ERROR] urls[4] = file:/Users/bryanhunt/.m2/repository/org/slf4j/jcl-over-slf4j/1.5.6/jcl-over-slf4j-1.5.6.jar
[ERROR] urls[5] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/reporting/maven-reporting-api/2.2.1/maven-reporting-api-2.2.1.jar
[ERROR] urls[6] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/doxia/doxia-sink-api/1.1/doxia-sink-api-1.1.jar
[ERROR] urls[7] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/doxia/doxia-logging-api/1.1/doxia-logging-api-1.1.jar
[ERROR] urls[8] = file:/Users/bryanhunt/.m2/repository/commons-cli/commons-cli/1.2/commons-cli-1.2.jar
[ERROR] urls[9] = file:/Users/bryanhunt/.m2/repository/org/codehaus/plexus/plexus-interactivity-api/1.0-alpha-4/plexus-interactivity-api-1.0-alpha-4.jar
[ERROR] urls[10] = file:/Users/bryanhunt/.m2/repository/org/sonatype/plexus/plexus-sec-dispatcher/1.3/plexus-sec-dispatcher-1.3.jar
[ERROR] urls[11] = file:/Users/bryanhunt/.m2/repository/org/sonatype/plexus/plexus-cipher/1.4/plexus-cipher-1.4.jar
[ERROR] urls[12] = file:/Users/bryanhunt/.m2/repository/org/codehaus/plexus/plexus-utils/3.0.22/plexus-utils-3.0.22.jar
[ERROR] urls[13] = file:/Users/bryanhunt/.m2/repository/commons-lang/commons-lang/2.3/commons-lang-2.3.jar
[ERROR] urls[14] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/enforcer/enforcer-api/1.4.1/enforcer-api-1.4.1.jar
[ERROR] urls[15] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/enforcer/enforcer-rules/1.4.1/enforcer-rules-1.4.1.jar
[ERROR] urls[16] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/shared/maven-common-artifact-filters/1.4/maven-common-artifact-filters-1.4.jar
[ERROR] urls[17] = file:/Users/bryanhunt/.m2/repository/org/beanshell/bsh/2.0b4/bsh-2.0b4.jar
[ERROR] urls[18] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/shared/maven-dependency-tree/2.2/maven-dependency-tree-2.2.jar
[ERROR] urls[19] = file:/Users/bryanhunt/.m2/repository/org/codehaus/plexus/plexus-component-annotations/1.5.5/plexus-component-annotations-1.5.5.jar
[ERROR] urls[20] = file:/Users/bryanhunt/.m2/repository/org/eclipse/aether/aether-util/0.9.0.M2/aether-util-0.9.0.M2.jar
[ERROR] urls[21] = file:/Users/bryanhunt/.m2/repository/org/codehaus/plexus/plexus-i18n/1.0-beta-6/plexus-i18n-1.0-beta-6.jar
[ERROR] urls[22] = file:/Users/bryanhunt/.m2/repository/org/apache/maven/plugin-testing/maven-plugin-testing-harness/1.3/maven-plugin-testing-harness-1.3.jar
[ERROR] urls[23] = file:/Users/bryanhunt/.m2/repository/org/codehaus/plexus/plexus-archiver/2.2/plexus-archiver-2.2.jar
[ERROR] urls[24] = file:/Users/bryanhunt/.m2/repository/org/codehaus/plexus/plexus-io/2.0.4/plexus-io-2.0.4.jar
[ERROR] urls[25] = file:/Users/bryanhunt/.m2/repository/junit/junit/4.11/junit-4.11.jar
[ERROR] urls[26] = file:/Users/bryanhunt/.m2/repository/org/hamcrest/hamcrest-core/1.3/hamcrest-core-1.3.jar
[ERROR] Number of foreign imports: 1
[ERROR] import: Entry[import  from realm ClassRealm[maven.api, parent: null]]
[ERROR]
[ERROR] -----------------------------------------------------
[ERROR] : begin 0, end 3, length 1
[ERROR] -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginContainerException

Warnings as errors - warning wrt conversion/use of Long in riak/client/core/query/timeseries/DescribeQueryResultParser.java breaks the build - it's deprecated as of Java 9 (installed by default on OSX). IMHO - at this point in product life-cycle better to generate a warning and have folk build the project than fail on something that will be a (potential) issue come Java 10 (and it's debatable whether there's any point in keeping the Riak TS code anyway).

DatatypeConverter is java.xml - can't rely on it being present - I don't know why apache commons codec wasn't used in the first place - every hack has it's price - in this case, it didn't build.

there's a reason why it's called 'internal' you can't depend on it existing in future versions - like now for example :-D

hard to see how this ever worked - it'll work now though.

mockito won't tolerate mocking, then not using the mock anymore - it throws  org.mockito.exceptions.misusing.UnnecessaryStubbingException - I've stubbed them out rather than delete in case it's necessary to reason about intent at some point in the future.

Started off with fixing bad call to verifyStatic (API has changed) then having spent about an hour figuring out what was wrong - UnfinishedVerificationException - it was never being hit anyway.

so why this file? die with fire

Feature/add java 9 support