Unable to import pandas when using the gtk3 backend in ipython
```
In [1]: %matplotlib gtk3

In [2]: import pandas
---------------------------------------------------------------------------
UnicodeDecodeError                        Traceback (most recent call last)
<ipython-input-2-38d4b0363d82> in <module>()
----> 1 import pandas

~/.local/lib/python3.6/site-packages/pandas/__init__.py in <module>()
     56 
     57 from pandas.util._print_versions import show_versions
---> 58 from pandas.io.api import *
     59 from pandas.util._tester import test
     60 import pandas.testing

~/.local/lib/python3.6/site-packages/pandas/io/api.py in <module>()
     17 from pandas.io.stata import read_stata
     18 from pandas.io.pickle import read_pickle, to_pickle
---> 19 from pandas.io.packers import read_msgpack, to_msgpack
     20 from pandas.io.gbq import read_gbq
     21 

~/.local/lib/python3.6/site-packages/pandas/io/packers.py in <module>()
     66 
     67 from pandas.io.msgpack import Unpacker as _Unpacker, Packer as _Packer, ExtType
---> 68 from pandas.util._move import (
     69     BadMove as _BadMove,
     70     move_into_mutable_buffer as _move_into_mutable_buffer,

UnicodeDecodeError: 'utf-8' codec can't decode byte 0x89 in position 3: invalid start byte
```

If I use tk or qt instead, this doesn't happen.