Relax safeguards on delete methods

Prior to this change, delete methods threw in any case where the
reference to a layer happened to be faulty. This is based on metadata
which, though always present in case of tile data (and necessary for
its deletion), might not be present. Lacking this metadata, we should
log information about the failure and delete any _attribute data we can.

s3/src/main/scala/geotrellis/spark/io/s3/S3AttributeStore.scala

@@ -98,7 +98,6 @@ class S3AttributeStore(val bucket: String, val prefix: String) extends BlobLayer
       .exists(_.getKey.endsWith(s"${AttributeStore.Fields.metadata}${SEP}${layerId.name}${SEP}${layerId.zoom}.json"))
 
   def delete(layerId: LayerId, attributeName: String): Unit = {
-    if(!layerExists(layerId)) throw new LayerNotFoundError(layerId)
     s3Client.deleteObject(bucket, attributePath(layerId, attributeName))
     clearCache(layerId, attributeName)
   }
@@ -112,7 +111,6 @@ class S3AttributeStore(val bucket: String, val prefix: String) extends BlobLayer
   }
 
   def delete(layerId: LayerId): Unit = {
-    if(!layerExists(layerId)) throw new LayerNotFoundError(layerId)
     layerKeys(layerId).foreach(s3Client.deleteObject(bucket, _))
     clearCache(layerId)
   }

s3/src/main/scala/geotrellis/spark/io/s3/S3LayerDeleter.scala

@@ -18,26 +18,29 @@ package geotrellis.spark.io.s3
 
 import geotrellis.spark.LayerId
 import geotrellis.spark.io._
+import geotrellis.util.LazyLogging
+
 import spray.json.JsonFormat
 import spray.json.DefaultJsonProtocol._
 
-class S3LayerDeleter(val attributeStore: AttributeStore) extends LayerDeleter[LayerId] {
+class S3LayerDeleter(val attributeStore: AttributeStore) extends LazyLogging with LayerDeleter[LayerId] {
 
   def getS3Client: () => S3Client = () => S3Client.DEFAULT
 
   def delete(id: LayerId): Unit = {
-    if (!attributeStore.layerExists(id)) throw new LayerNotFoundError(id)
-    val header = try {
-      attributeStore.readHeader[S3LayerHeader](id)
+    try {
+      val header = attributeStore.readHeader[S3LayerHeader](id)
+      val bucket = header.bucket
+      val prefix = header.key
+      val s3Client = getS3Client()
+
+      s3Client.deleteListing(bucket, s3Client.listObjects(bucket, prefix))
     } catch {
-      case e: AttributeNotFoundError => throw new LayerDeleteError(id).initCause(e)
+      case e: AttributeNotFoundError =>
+        logger.info(s"Metadata for $id was not found. Any associated layer data (if any) will require manual deletion")
+      case e: Exception =>
+        throw e
     }
-
-    val bucket = header.bucket
-    val prefix = header.key
-    val s3Client = getS3Client()
-
-    s3Client.deleteListing(bucket, s3Client.listObjects(bucket, prefix))
     attributeStore.delete(id)
   }
 }