Description of problem:
The edit key "e" and "a" in grub doesn't work while using pygrub + grub2.

Version-Release number of selected component (if applicable):
xen-3.0.3-135.el5

How reproducible:
100%

Steps to Reproduce:
1. Install a Fedora 16 PV guest (using GPT or msdos partition )
2. boot up the guest and connect to the console
   # xm create -c fedora
3. press "e" or "a" in pygrub to modify the kernel arguments
  
Actual results:

# xm creat -c fedora
Using config file "./fedora".
Using <class 'grub.GrubConf.Grub2ConfigFile'> to parse /grub2/grub.cfg
WARNING:root:Unknown image directive load_video
WARNING:root:Unknown directive source
Traceback (most recent call last):
  File "/usr/bin/pygrub", line 714, in ?
    chosencfg = run_grub(file, entry, fs)
  File "/usr/bin/pygrub", line 565, in run_grub
    curses.wrapper(run_main)
  File "/usr/lib64/python2.4/curses/wrapper.py", line 44, in wrapper
    return func(stdscr, *args, **kwds)
  File "/usr/bin/pygrub", line 561, in run_main
    sel = g.run()
  File "/usr/bin/pygrub", line 436, in run
    self.run_main(timeout)
  File "/usr/bin/pygrub", line 505, in run_main
    self.edit_entry(img)
  File "/usr/bin/pygrub", line 298, in edit_entry
    self.entry_win.addstr(idx, 2, l, attr)
_curses.error: addstr() returned ERR
No handlers could be found for logger "xend"
Error: Boot loader didn't return any data!
Usage: xm create <ConfigFile> [options] [vars]

Expected results:
The "e" and "a" keys should work in pygrub

Additional info:
1. This defect happen with both gpt and msdos partition.
2. No problem for just booting up the fedora 16 pv guest with pygrub