BUG: UnicodeEncodeError in test_to_latex_filename (pandas.tests.test_format.TestDataFrameFormatting)
Getting this error if (and I think only if) `LANG` is not defined or not set to any `utf8`-conforming value on 0.18.0rc1 (Mac OS X 10.10, python 3.4.4, numpy 0.11.0b3):

```
ERROR: test_to_latex_filename (pandas.tests.test_format.TestDataFrameFormatting)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/scratch.noindex/fink.build/pandas-py34-0.18.0rc1-1/pandas-0.18.0rc1/pandas/tests/test_format.py", line 2614, in test_to_latex_filename
    df.to_latex(path)
  File "/scratch.noindex/fink.build/pandas-py34-0.18.0rc1-1/pandas-0.18.0rc1/pandas/core/frame.py", line 1593, in to_latex
    encoding=encoding)
  File "/scratch.noindex/fink.build/pandas-py34-0.18.0rc1-1/pandas-0.18.0rc1/pandas/core/format.py", line 641, in to_latex
    latex_renderer.write_result(f)
  File "/scratch.noindex/fink.build/pandas-py34-0.18.0rc1-1/pandas-0.18.0rc1/pandas/core/format.py", line 877, in write_result
    buf.write(' & '.join(crow))
UnicodeEncodeError: 'ascii' codec can't encode character '\xdf' in position 7: ordinal not in range(128)
```

Don't know about the inner workings of this test; if there are any open files involved, this might be relevant: https://github.com/scipy/scipy/issues/5694
