#1000 live: check imageCreate for non-zero return code

When running image_create operation an underlying script "imageCreate"
is called using the subprocess python module. This script may fail, for
example if the repository in which the image is to be stored has no
sufficent capacity.

Check for non-zero when the imageCreate process has finished.

src/live/ogOperations.py

@@ -240,6 +240,9 @@ class OgLiveOperations:
         except:
             raise ValueError('Error: Incorrect command value')
 
+        if ogRest.proc.returncode != 0:
+            raise ValueError('Error: Image creation failed')
+
         with open('/tmp/image.info') as file_info:
             line = file_info.readline().rstrip()