Remove most uses of module string
diff --git a/Lib/fontTools/cffLib.py b/Lib/fontTools/cffLib.py
index d0c35f2..2bccee6 100644
--- a/Lib/fontTools/cffLib.py
+++ b/Lib/fontTools/cffLib.py
@@ -6,7 +6,6 @@
 
 import struct
 from fontTools.misc import sstruct
-import string
 from fontTools.misc import psCharStrings
 from fontTools.misc.textTools import safeEval
 
@@ -896,7 +895,7 @@
 	if isCID:
 		for i in range(numGlyphs - 1):
 			CID = readCard16(file)
-			charset.append("cid" + string.zfill(str(CID), 5) )
+			charset.append("cid" + str(CID).zfill(5))
 	else:
 		for i in range(numGlyphs - 1):
 			SID = readCard16(file)
@@ -915,7 +914,7 @@
 		nLeft = nLeftFunc(file)
 		if isCID:
 			for CID in range(first, first+nLeft+1):
-				charset.append("cid" + string.zfill(str(CID), 5) )
+				charset.append("cid" + str(CID).zfill(5))
 		else:
 			for SID in range(first, first+nLeft+1):
 				charset.append(strings[SID])