[t2CharStringPen] raise ValueError if tolerance not in range 0 <= t <= 0.5

Lib/fontTools/pens/t2CharStringPen.py

@@ -67,7 +67,8 @@ class RelativeCoordinatePen(BasePen):
 
 
 def makeRoundFunc(tolerance):
-    assert 0 <= tolerance <= 0.5
+    if not (0 <= tolerance <= 0.5):
+        raise ValueError("Rounding tolerance out of range: %g" % tolerance)
 
     def _round(number):
         if tolerance == 0:

Lib/fontTools/pens/t2CharStringPen_test.py

@@ -6,6 +6,13 @@ import unittest
 
 class T2CharStringPenTest(unittest.TestCase):
 
+    def __init__(self, methodName):
+        unittest.TestCase.__init__(self, methodName)
+        # Python 3 renamed assertRaisesRegexp to assertRaisesRegex,
+        # and fires deprecation warnings if a program uses the old name.
+        if not hasattr(self, "assertRaisesRegex"):
+            self.assertRaisesRegex = self.assertRaisesRegexp
+
     def assertAlmostEqualProgram(self, expected, actual):
         self.assertEqual(len(expected), len(actual))
         for i1, i2 in zip(expected, actual):
@@ -106,6 +113,13 @@ class T2CharStringPenTest(unittest.TestCase):
              'endchar'],
             charstring.program)
 
+    def test_invalid_tolerance(self):
+        for value in (-0.1, 0.6):
+            self.assertRaisesRegex(
+                ValueError,
+                "Rounding tolerance out of range",
+                T2CharStringPen, None, {}, roundTolerance=value)
+
 
 if __name__ == '__main__':
     import sys