test_json:test_round_trip_exception_  fails on python3 in windows
The API design issue discussed in #5655 again. pd.read_json guesses that a 150KB long string is a filename. 

``` python

======================================================================
ERROR: test_round_trip_exception_ (pandas.io.tests.test_json.test_pandas.TestPandasContainer)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "C:\workspace\pandas_tests@2\BITS\64\PYTHONVER\33\pandas\util\testing.py", line 1057, in network_wrapper
    return t(*args, **kwargs)
  File "C:\workspace\pandas_tests@2\BITS\64\PYTHONVER\33\pandas\io\tests\test_json\test_pandas.py", line 593, in test_round_trip_exception_
    result = pd.read_json(s)
  File "C:\workspace\pandas_tests@2\BITS\64\PYTHONVER\33\pandas\io\json.py", line 176, in read_json
    if os.path.exists(filepath_or_buffer):
  File "c:\envs\33-64\lib\genericpath.py", line 18, in exists
    os.stat(path)
nose.proxy.ValueError: ValueError: path too long for Windows
-------------------- >> begin captured stdout << ---------------------
Failed: ValueError('path too long for Windows',)

--------------------- >> end captured stdout << ----------------------

```
