commit 14cd0c07d871f821b3cac37b5c59c5c152b7e9ff
Author: beejeebus <justin.p.randell@gmail.com>
Date:   Mon Jan 7 02:27:43 2019 +0000

    Return the file path from the underlying filesystem service.

diff --git a/core/modules/migrate/src/Plugin/migrate/process/FileCopy.php b/core/modules/migrate/src/Plugin/migrate/process/FileCopy.php
index 33b3959ba2..f69ab140f3 100644
--- a/core/modules/migrate/src/Plugin/migrate/process/FileCopy.php
+++ b/core/modules/migrate/src/Plugin/migrate/process/FileCopy.php
@@ -175,17 +175,16 @@ protected function writeFile($source, $destination, $replace = FileSystemInterfa
     // Check if there is a destination available for copying. If there isn't,
     // it already exists at the destination and the replace flag tells us to not
     // replace it. In that case, return the original destination.
-    if (!($final_destination = $this->fileSystem->getDestinationFilename($destination, $replace))) {
+    if ($this->fileSystem->getDestinationFilename($destination, $replace) === FALSE) {
       return $destination;
     }
     try {
       if ($this->configuration['move']) {
-        $this->fileSystem->move($source, $destination, $replace);
+        return $this->fileSystem->move($source, $destination, $replace);
       }
       else {
-        $this->fileSystem->copy($source, $destination, $replace);
+        return $this->fileSystem->copy($source, $destination, $replace);
       }
-      return $destination;
     }
     catch (FileException $e) {
       return FALSE;