Catch only non-fatal errors loading config (#97)

src/main/scala/com/sky/kafka/topicloader/config/config.scala

@@ -5,18 +5,20 @@ import cats.implicits._
 import com.typesafe.config.ConfigException
 
 import scala.util.Try
+import scala.util.control.NonFatal
 
 package object config {
   type ValidationResult[A] = ValidatedNec[ConfigException, A]
 
   implicit class TryOps[A](t: Try[A]) {
-    def validate(path: String): ValidationResult[A] = t.toEither.validate(path)
-  }
-
-  implicit class EitherOps[A](e: Either[Throwable, A]) {
-    def validate(path: String): ValidationResult[A] = e.leftMap {
+    private[topicloader] def validate(path: String): ValidationResult[A] = t.toEither.leftMap {
       case ce: ConfigException => ce
-      case e: Throwable        => new ConfigException.BadValue(path, e.getMessage)
+      case NonFatal(e)         => new ConfigException.BadValue(path, e.getMessage)
     }.toValidatedNec
   }
+
+  implicit class EitherOps[A](e: Either[IllegalArgumentException, A]) {
+    private[topicloader] def validate(path: String): ValidationResult[A] =
+      e.leftMap(e => new ConfigException.BadValue(path, e.getMessage)).toValidatedNec
+  }
 }

src/test/scala/integration/TopicLoaderIntSpec.scala

@@ -291,7 +291,7 @@ class TopicLoaderIntSpec extends IntegrationSpecBase {
       config.topicLoader.bufferSize.value shouldBe 10
     }
 
-    "fail to load a valid config" in new TestContext {
+    "fail to load an invalid config" in new TestContext {
       override implicit lazy val system: ActorSystem = ActorSystem(
         "test-actor-system",
         ConfigFactory.parseString(