use RecursionError, and provide an alias for RuntimeError for Py2

Lib/fontTools/misc/py23.py

@@ -7,7 +7,7 @@ import sys
 __all__ = ['basestring', 'unicode', 'unichr', 'byteord', 'bytechr', 'BytesIO',
 		'StringIO', 'UnicodeIO', 'strjoin', 'bytesjoin', 'tobytes', 'tostr',
 		'tounicode', 'Tag', 'open', 'range', 'xrange', 'round', 'Py23Error',
-		'SimpleNamespace', 'zip']
+		'SimpleNamespace', 'zip', 'RecursionError']
 
 
 class Py23Error(NotImplementedError):
@@ -514,6 +514,12 @@ else:
 		_stream = "stderr"
 
 
+try:
+	RecursionError = RecursionError
+except NameError:
+	RecursionError = RuntimeError
+
+
 if __name__ == "__main__":
 	import doctest, sys
 	sys.exit(doctest.testmod().failed)

Lib/fontTools/ttLib/tables/_g_l_y_f.py

@@ -843,7 +843,7 @@ class Glyph(object):
 				g = glyfTable[compo.glyphName]
 				try:
 					coordinates, endPts, flags = g.getCoordinates(glyfTable)
-				except RuntimeError:
+				except RecursionError:
 					raise ttLib.TTLibError("glyph '%s' contains a recursive component reference" % compo.glyphName)
 				if hasattr(compo, "firstPt"):
 					# move according to two reference points