[macCreatorType] fix KeyError raised by old version of xattr module

in version 0.6.4 (installed on OS X 10.10 python lib/extras) it raises
KeyError, whereas in the latest version available fom PyPI (v0.7.8) it
raises IOError.

Fixes issue in https://github.com/googlei18n/nototools/issues/113

Lib/fontTools/misc/macCreatorType.py

@@ -21,7 +21,7 @@ def getMacCreatorAndType(path):
 	if xattr is not None:
 		try:
 			finderInfo = xattr.getxattr(path, 'com.apple.FinderInfo')
-		except IOError:
+		except (KeyError, IOError):
 			pass
 		else:
 			fileType = Tag(finderInfo[:4])