Added SEEK_* constants. Fixes #711830.
diff --git a/Lib/os.py b/Lib/os.py
index 65b1830..d3b9a8d 100644
--- a/Lib/os.py
+++ b/Lib/os.py
@@ -29,7 +29,8 @@
 
 # Note:  more names are added to __all__ later.
 __all__ = ["altsep", "curdir", "pardir", "sep", "pathsep", "linesep",
-           "defpath", "name", "path", "devnull"]
+           "defpath", "name", "path", "devnull",
+           "SEEK_SET", "SEEK_CUR", "SEEK_END"]
 
 def _get_exports_list(module):
     try:
@@ -135,6 +136,12 @@
 
 del _names
 
+# Python uses fixed values for the SEEK_ constants; they are mapped
+# to native constants if necessary in posixmodule.c
+SEEK_SET = 0
+SEEK_CUR = 1
+SEEK_END = 2
+
 #'
 
 # Super directory utilities.