Index: test_fileio.py
===================================================================
--- test_fileio.py	(revision 81326)
+++ test_fileio.py	(working copy)
@@ -172,7 +172,7 @@
 
     @ClosedFDRaises
     def testErrnoOnClosedWrite(self, f):
-        f.write('a')
+        f.write(b'a')
 
     @ClosedFDRaises
     def testErrnoOnClosedSeek(self, f):