Correct call to `sys.exit()`

It should be `sys.exit()` not `os.exit()`.

Change-Id: Iaeeef456ddf2d17f5df2b712e50e3630bed856c3

pager.py

@@ -50,7 +50,7 @@ def RunPager(globalConfig):
     _BecomePager(pager)
   except Exception:
     print >>sys.stderr, "fatal: cannot start pager '%s'" % pager
-    os.exit(255)
+    sys.exit(255)
 
 def _SelectPager(globalConfig):
   try: