read_msgpack returns garbage for non-existing files in python2
#### Code Sample, a copy-pastable example if possible

```python
In [1]: import pandas as pd

In [2]: pd.__version__
Out[2]: u'0.19.2'

In [3]: pd.read_msgpack('/tmp/bla.txt')
Out[3]: [47, 116, 109, 112, 47, 98, 108, 97, 46, 116, 120, 116]
```

That file does not exist.

The same code with the same version on python 3 correctly raises an exception.

#### Problem description

Reading a non existing file returns a list of integers instead of failing if pandas is used in python 2. This makes detecting error quite hard.

#### Expected Output

An exception.

#### Output of ``pd.show_versions()``

<details>

```
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.13.final.0
python-bits: 64
OS: Linux
OS-release: 4.9.6-1-ARCH
machine: x86_64
processor: 
byteorder: little
LC_ALL: None
LANG: en_US.utf8
LOCALE: None.None

pandas: 0.19.2
nose: 1.3.7
pip: 9.0.1
setuptools: 34.1.0
Cython: None
numpy: 1.11.3
scipy: 0.18.1
statsmodels: None
xarray: None
IPython: 5.1.0
sphinx: None
patsy: None
dateutil: 2.6.0
pytz: 2016.10
blosc: None
bottleneck: 1.2.0
tables: 3.3.0
numexpr: 2.6.1
matplotlib: 1.5.3
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: None
jinja2: 2.9.5
boto: None
pandas_datareader: None
```

</details>
