[MINOR] Only Test errorprone-checks on JDK8 (#89)

* [MINOR] Only Test errorprone-checks on JDK8

The current version of errorprone causes errors when compiled with Java
11. The next version causes causes problems with Java 8.  So for now
keep the old version and only test when compiled with Java 8 (which
is the current Jenkins version). When the test is skipped an info log is sent.

Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

errorprone-checks/build.gradle

@@ -19,7 +19,7 @@ dependencies {
   implementation "com.google.errorprone:error_prone_core"
   implementation "com.google.errorprone:error_prone_annotation"
 
-  implementation      "com.google.auto.service:auto-service:1.0-rc4"
+  implementation "com.google.auto.service:auto-service:1.0-rc4"
   annotationProcessor "com.google.auto.service:auto-service:1.0-rc4"
 
   testImplementation "junit:junit"
@@ -30,8 +30,13 @@ dependencies {
 }
 
 test {
-  if (JavaVersion.current().isJava8()) {
-    jvmArgs "-Xbootclasspath/p:${configurations.epJavac.asPath}"
+  if (!JavaVersion.current().isJava8()) {
+    enabled = false
+    logger.info("Disabling {} because errorprone tests always fail in Java {}",
+      project.name, JavaVersion.current().majorVersion)
   }
+
+  jvmArgs "-Xbootclasspath/p:${configurations.epJavac.asPath}"
+
   testLogging { showStandardStreams = true }
 }