Better error messages

[J535D165]

404 results in a error like this:

In [1]: import cbsodata
   ...: import pandas as pd
   ...: data = pd.DataFrame(cbsodata.get_data('47015NED'))
   ...: print(data.head())
   ...: 
/Users/jonathandebruin/.pyenv/versions/anaconda3-5.0.1/lib/python3.6/importlib/_bootstrap.py:219: RuntimeWarning: numpy.dtype size changed, may indicate binary incompatibility. Expected 96, got 88
  return f(*args, **kwds)
---------------------------------------------------------------------------
JSONDecodeError                           Traceback (most recent call last)
<ipython-input-1-7c8e94229f87> in <module>()
      1 import cbsodata
      2 import pandas as pd
----> 3 data = pd.DataFrame(cbsodata.get_data('47015NED'))
      4 print(data.head())

~/.pyenv/versions/anaconda3-5.0.1/lib/python3.6/site-packages/cbsodata.py in get_data(table_id, dir, typed, select, filters)
    277 
    278     metadata = download_data(table_id, dir=dir, typed=typed,
--> 279                              select=select, filters=filters)
    280 
    281     if "TypedDataSet" in metadata.keys():

~/.pyenv/versions/anaconda3-5.0.1/lib/python3.6/site-packages/cbsodata.py in download_data(table_id, dir, typed, select, filters)
    155 
    156     # http://opendata.cbs.nl/ODataApi/OData/37506wwm?$format=json
--> 157     metadata_tables = _download_metadata(table_id, "")
    158 
    159     # The names of the tables with metadata

~/.pyenv/versions/anaconda3-5.0.1/lib/python3.6/site-packages/cbsodata.py in _download_metadata(table_id, metadata_name, select, filters)
     80         r = requests.get(url, params=params)
     81 
---> 82         res = r.json(encoding='utf-8')
     83         res_value = res['value']
     84 

~/.pyenv/versions/anaconda3-5.0.1/lib/python3.6/site-packages/requests/models.py in json(self, **kwargs)
    894                     # used.
    895                     pass
--> 896         return complexjson.loads(self.text, **kwargs)
    897 
    898     @property

~/.pyenv/versions/anaconda3-5.0.1/lib/python3.6/site-packages/simplejson/__init__.py in loads(s, encoding, cls, object_hook, parse_float, parse_int, parse_constant, object_pairs_hook, use_decimal, **kw)
    533             raise TypeError("use_decimal=True implies parse_float=Decimal")
    534         kw['parse_float'] = Decimal
--> 535     return cls(encoding=encoding, **kw).decode(s)
    536 
    537 

~/.pyenv/versions/anaconda3-5.0.1/lib/python3.6/site-packages/simplejson/decoder.py in decode(self, s, _w, _PY3)
    368         if _PY3 and isinstance(s, bytes):
    369             s = str(s, self.encoding)
--> 370         obj, end = self.raw_decode(s)
    371         end = _w(s, end).end()
    372         if end != len(s):

~/.pyenv/versions/anaconda3-5.0.1/lib/python3.6/site-packages/simplejson/decoder.py in raw_decode(self, s, idx, _w, _PY3)
    398             elif ord0 == 0xef and s[idx:idx + 3] == '\xef\xbb\xbf':
    399                 idx += 3
--> 400         return self.scan_once(s, idx=_w(s, idx).end())

JSONDecodeError: Expecting value: line 1 column 1 (char 0)