Workaround a libguestfs e2fsck bug

Workaround the bug that libguestfs may raise a RuntimeError even if the
command runs successfully, due to the fact that the command exited with
non-zero exit status.

image_creator/image.py

 # -*- coding: utf-8 -*-
 #
-# Copyright (C) 2011-2014 GRNET S.A.
+# Copyright (C) 2011-2015 GRNET S.A.
 #
 # This program is free software: you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -361,10 +361,17 @@ class Image(object):
 
         part_dev = "%s%d" % (self.guestfs_device, last_part['part_num'])
 
-        if self.check_guestfs_version(1, 15, 17) >= 0:
-            self.g.e2fsck(part_dev, forceall=1)
-        else:
-            self.g.e2fsck_f(part_dev)
+        try:
+            if self.check_guestfs_version(1, 15, 17) >= 0:
+                self.g.e2fsck(part_dev, forceall=1)
+            else:
+                self.g.e2fsck_f(part_dev)
+        except RuntimeError as e:
+            # There is a bug in some versions of libguestfs and a RuntimeError
+            # is thrown although the command has successfully corrected the
+            # found file system errors.
+            if e.message.find('***** FILE SYSTEM WAS MODIFIED *****') == -1:
+                raise
 
         self.g.resize2fs_M(part_dev)