Exception when adding a unicode margins_name in pivot_table

[spapas]

Code Sample, a copy-pastable example if possible

This throws UnicodeDecodeError in python2

pd.pivot_table(pd.DataFrame({'foo': [1,2,3]}), index=['foo'], aggfunc=len, margins=True, margins_name=u'Δοκιμή')

Expected Output

Not throwing exception!

output of pd.show_versions()

INSTALLED VERSIONS
------------------
commit: None
python: 2.7.11.final.0
python-bits: 32
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 58 Stepping 9, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None

pandas: 0.18.1
nose: None
pip: 8.1.2
setuptools: 20.10.1
Cython: None
numpy: 1.11.0
scipy: None
statsmodels: None
xarray: None
IPython: None
sphinx: None
patsy: None
dateutil: 2.5.2
pytz: 2016.4
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: None
openpyxl: None
xlrd: 0.9.4
xlwt: 1.0.0
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: None
pymysql: None
psycopg2: 2.6.1 (dt dec pq3 ext)
jinja2: None
boto: None
pandas_datareader: None

The above is a well-known problem when mixing unicode and non-unicode strings in python2: The fix (for python 2) is very simple, just add a u in front of the exception_msg string literal in https://github.com/pydata/pandas/blob/master/pandas/tools/pivot.py#L178 i.e line 178 should be exception_msg = u'Conflicting name "{0}" in margins'.format(margins_name)

I am not sure what's the correct way to fix that in python 3 and a python2-3 compatible way so I won't provide a PR for that.

[jreback]

mixing of str with unicode is NEVER recommended.

can check the Index if its inferred_type == 'unicode' if the passed value is also unicode, otherwise could raise an error. So I'll mark this as a better error message.

[mpenkov]

@sinhrks I'll start with this one, if it's OK.

[mpenkov]

I could reproduce the problem. This is the error I'm seeing:

(pandas)bash-3.2$ python
Python 2.7.13 (default, Jun  2 2017, 06:36:47)
[GCC 4.2.1 Compatible Apple LLVM 8.1.0 (clang-802.0.42)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import pandas as pd
>>> pd.pivot_table(pd.DataFrame({'foo': [1,2,3]}), index=['foo'], aggfunc=len, margins=True, margins_name=u'Δοκιμή')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "pandas/core/reshape/pivot.py", line 126, in pivot_table
    margins_name=margins_name, fill_value=fill_value)
  File "pandas/core/reshape/pivot.py", line 148, in _add_margins
    msg = 'Conflicting name "{name}" in margins'.format(name=margins_name)
UnicodeEncodeError: 'ascii' codec can't encode characters in position 0-5: ordinal not in range(128)