*** difflib.py
--- difflib.py
***************
*** 573,584 ****
  
          codes = self.get_opcodes()
          # Fixup leading and trailing groups if they show no changes.
!         if codes[0][0] == 'equal':
!             tag, i1, i2, j1, j2 = codes[0]
!             codes[0] = tag, max(i1, i2-n), i2, max(j1, j2-n), j2
!         if codes[-1][0] == 'equal':
!             tag, i1, i2, j1, j2 = codes[-1]
!             codes[-1] = tag, i1, min(i2, i1+n), j1, min(j2, j1+n)
  
          nn = n + n
          group = []
--- 573,585 ----
  
          codes = self.get_opcodes()
          # Fixup leading and trailing groups if they show no changes.
!         if codes:
!             if codes[0][0] == 'equal':
!                 tag, i1, i2, j1, j2 = codes[0]
!                 codes[0] = tag, max(i1, i2-n), i2, max(j1, j2-n), j2
!             if codes[-1][0] == 'equal':
!                 tag, i1, i2, j1, j2 = codes[-1]
!                 codes[-1] = tag, i1, min(i2, i1+n), j1, min(j2, j1+n)
  
          nn = n + n
          group = []

###