From be898ec6f9079f5faa45b8abc3204055dca10d28 Mon Sep 17 00:00:00 2001
From: Tom Archer <tom.archer@daltonmaag.com>
Date: Wed, 20 Jan 2021 14:30:49 +0000
Subject: [PATCH] Change ValueError to OpenTypeLibError

---
 Lib/fontTools/otlLib/builder.py | 2 +-
 Tests/otlLib/builder_test.py    | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/Lib/fontTools/otlLib/builder.py b/Lib/fontTools/otlLib/builder.py
index 5d16b83c2..029aa3fc5 100644
--- a/Lib/fontTools/otlLib/builder.py
+++ b/Lib/fontTools/otlLib/builder.py
@@ -2575,7 +2575,7 @@ class ClassDefBuilder(object):
         self.classes_.add(glyphs)
         for glyph in glyphs:
             if glyph in self.glyphs_:
-                raise ValueError(f"Glyph {glyph} is already present in class.")
+                raise OpenTypeLibError(f"Glyph {glyph} is already present in class.", None)
             self.glyphs_[glyph] = glyphs
 
     def classes(self):
diff --git a/Tests/otlLib/builder_test.py b/Tests/otlLib/builder_test.py
index 6bd05615b..3ea5a7459 100644
--- a/Tests/otlLib/builder_test.py
+++ b/Tests/otlLib/builder_test.py
@@ -2,7 +2,7 @@ import io
 import struct
 from fontTools.misc.fixedTools import floatToFixed
 from fontTools.misc.testTools import getXML
-from fontTools.otlLib import builder
+from fontTools.otlLib import builder, error
 from fontTools import ttLib
 from fontTools.ttLib.tables import otTables
 import pytest
@@ -1104,7 +1104,7 @@ class ClassDefBuilderTest(object):
     def test_add_exception(self):
         b = builder.ClassDefBuilder(useClass0=True)
         b.add({"a", "b", "c"})
-        with pytest.raises(ValueError):
+        with pytest.raises(error.OpenTypeLibError):
             b.add({"a", "d"})