eula file typo

its OPEN-EULA.txt not OPEN_EULA.txt
diff --git a/build_images.py b/build_images.py
index 1ae0a43..9aa47be 100755
--- a/build_images.py
+++ b/build_images.py
@@ -40,7 +40,7 @@
         if eula:
             self.eula = 'EULA.txt'
         else:
-            self.eula = 'OPEN_EULA.txt'
+            self.eula = 'OPEN-EULA.txt'
         self.pre_inst_script = pre_inst_script
 
     def do_eula(self, imgfile):