[2.7] remove unused import (GH-5040). (#5043)

(cherry picked from commit e325608740bee161ca7fefd09463d63099efa1b8)
diff --git a/Lib/lib2to3/patcomp.py b/Lib/lib2to3/patcomp.py
index 00679b2..49ed668 100644
--- a/Lib/lib2to3/patcomp.py
+++ b/Lib/lib2to3/patcomp.py
@@ -11,7 +11,6 @@
 __author__ = "Guido van Rossum <guido@python.org>"
 
 # Python imports
-import os
 import StringIO
 
 # Fairly local imports