Fix a typo of debug log in scenario/manager.py

This commit fixes a incorrect word grammatically.

Change-Id: Id38069cfb107a0c6a6c6de4543e3a899532d916e
diff --git a/tempest/scenario/manager.py b/tempest/scenario/manager.py
index 02a3c9d..adc24ec 100644
--- a/tempest/scenario/manager.py
+++ b/tempest/scenario/manager.py
@@ -590,7 +590,7 @@
                                             properties={'disk_format':
                                                         'qcow2'})
         except IOError:
-            LOG.debug("A qcow2 image was not got. Try to get a uec image.")
+            LOG.debug("A qcow2 image was not found. Try to get a uec image.")
             kernel = self._image_create('scenario-aki', 'aki', aki_img_path)
             ramdisk = self._image_create('scenario-ari', 'ari', ari_img_path)
             properties = {