pydata/pandas — pull request #4881 by jreback (2013-09-19 12:23:50+00:00)
Title: BUG: bug in getitem with a duplicate index when using where (GH4879)

raising previously as this was not handled properly

```
In [1]: df = DataFrame(np.arange(12).reshape(3,4), columns=['A', 'B', 'C', 'D'],dtype='float64')

In [2]: df
Out[2]:
A B C D
0 0 1 2 3
1 4 5 6 7
2 8 9 10 11

In [3]: df[df.C>6]
Out[3]:
A B C D
2 8 9 10 11

In [4]: df = DataFrame(np.arange(12).reshape(3,4), columns=['A', 'A', 'C', 'D'],dtype='float64')

In [5]: df
Out[5]:
A A C D
0 0 1 2 3
1 4 5 6 7
2 8 9 10 11

In [6]: df[df.C>6]
Out[6]:
A A C D
2 8 9 10 11
```