Future.recover does not catch exceptions that are thrown inside a CompletableFuture

I've been using the aws dynamodb async sdk, but I find that I cannot catch exceptions after I convert a CompletableFuture to Scala.
When I run

    client
      .createTable(tableSchema.createTableRequest(tableName))
      .thenApply[Unit](_ => Unit)
      .exceptionally {
        case _: Throwable => // exception is now property handled
      }

I can successfully catch the exception.

However when I run

     import scala.compat.java8.FutureConverters.toScala

    val cf = client
      .createTable(tableSchema.createTableRequest(tableName))
    toScala(cf).recover {
      case _: Throwable => // never gets executed
    }

I cannot actually catch the exception. Any clues on why?

Start with scala.compat.java8.FutureConverters.toScala and compare its exception behavior with CompletableFuture.exceptionally using the examples in the issue. Trace how exceptions from the CompletableFuture are propagated, then verify that Future.recover handles them as expected.