...

src/calibre/utils/fonts/sfnt/container.py

@@ -14,9 +14,7 @@ from io import BytesIO
 from calibre.utils.fonts.utils import (get_tables, checksum_of_block,
         verify_checksums)
 from calibre.utils.fonts.sfnt import align_block
-
-class UnsupportedFont(ValueError):
-    pass
+from calibre.utils.fonts.sfnt.errors import UnsupportedFont
 
 class UnknownTable(object):
 

src/calibre/utils/fonts/sfnt/errors.py

@@ -0,0 +1,12 @@
+#!/usr/bin/env python
+# vim:fileencoding=UTF-8:ts=4:sw=4:sta:et:sts=4:fdm=marker:ai
+from __future__ import (unicode_literals, division, absolute_import,
+                        print_function)
+
+__license__   = 'GPL v3'
+__copyright__ = '2012, Kovid Goyal <kovid at kovidgoyal.net>'
+__docformat__ = 'restructuredtext en'
+
+class UnsupportedFont(ValueError):
+    pass
+