Error and failure in nosetests (Ubuntu 12.04)
```
======================================================================
ERROR: test_map (pandas.tseries.tests.test_period.TestPeriodIndex)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/arthur/python-packages/pandas/pandas/tseries/tests/test_period.py", line 1523, in test_map
    assert_array_equal(result, expected)
  File "/usr/local/lib/python2.7/dist-packages/numpy/testing/utils.py", line 753, in assert_array_equal
    verbose=verbose, header='Arrays are not equal')
  File "/usr/local/lib/python2.7/dist-packages/numpy/testing/utils.py", line 612, in assert_array_compare
    x_isnan[x_isna] = False
  File "/home/arthur/python-packages/pandas/pandas/core/index.py", line 282, in __setitem__
    raise Exception(str(self.__class__) + ' object is immutable')
Exception: <class 'pandas.tseries.period.PeriodIndex'> object is immutable

======================================================================
FAIL: test_unicode_index (pandas.io.tests.test_pytables.TestHDFStore)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/arthur/python-packages/pandas/pandas/io/tests/test_pytables.py", line 661, in test_unicode_index
    self._check_roundtrip(s, tm.assert_series_equal)
  File "/home/arthur/python-packages/pandas/pandas/io/tests/test_pytables.py", line 566, in _check_roundtrip
    comparator(retrieved, obj, **kwargs)
  File "/home/arthur/python-packages/pandas/pandas/util/testing.py", line 129, in assert_series_equal
    assert(left.index.equals(right.index))
AssertionError
```
