title: Pandas returns "Passed header names mismatches usecols" error
body: <p>The following works as expected. There are 190 columns that are all read in perfectly.</p>
  
  <pre class="lang-python prettyprint-override"><code>pd.read_csv("data.csv", 
               header=None,
               names=columns,
               # usecols=columns[:10], 
               nrows=10
               )
  </code></pre>
  
  <p>I have used the usecols argument before, so I am perplexed as to why this is no longer working for me. I would guess that simply slicing the first 10 column names would trivially work, but I continue to get the "Passed header names mismatches usecols" error. </p>
  
  <p>I am using pandas 0.16.2.</p>
  
  <pre class="lang-python prettyprint-override"><code>pd.read_csv("data.csv", 
               header=None,
               names=columns,
               usecols=columns[:10], 
               nrows=10
               )
  </code></pre>
  
  <p>Traceback</p>
  
  <pre class="lang-python prettyprint-override"><code>---------------------------------------------------------------------------
  ValueError                                Traceback (most recent call last)
  &lt;ipython-input-44&gt; in &lt;module&gt;()
        3                     nrows=10,
        4                     header=None,
  ----&gt; 5                     names=columns,
        6                     )
  
  /.../lib/python2.7/site-packages/pandas/io/parsers.pyc in parser_f(filepath_or_buffer, sep, dialect, compression, doublequote, escapechar, quotechar, quoting, skipinitialspace, lineterminator, header, index_col, names, prefix, skiprows, skipfooter, skip_footer, na_values, na_fvalues, true_values, false_values, delimiter, converters, dtype, usecols, engine, delim_whitespace, as_recarray, na_filter, compact_ints, use_unsigned, low_memory, buffer_lines, warn_bad_lines, error_bad_lines, keep_default_na, thousands, comment, decimal, parse_dates, keep_date_col, dayfirst, date_parser, memory_map, float_precision, nrows, iterator, chunksize, verbose, encoding, squeeze, mangle_dupe_cols, tupleize_cols, infer_datetime_format, skip_blank_lines)
      472                     skip_blank_lines=skip_blank_lines)
      473 
  --&gt; 474         return _read(filepath_or_buffer, kwds)
      475 
      476     parser_f.__name__ = name
  
  /.../lib/python2.7/site-packages/pandas/io/parsers.pyc in _read(filepath_or_buffer, kwds)
      248 
      249     # Create the parser.
  --&gt; 250     parser = TextFileReader(filepath_or_buffer, **kwds)
      251 
      252     if (nrows is not None) and (chunksize is not None):
  
  /.../lib/python2.7/site-packages/pandas/io/parsers.pyc in __init__(self, f, engine, **kwds)
      564             self.options['has_index_names'] = kwds['has_index_names']
      565 
  --&gt; 566         self._make_engine(self.engine)
      567 
      568     def _get_options_with_defaults(self, engine):
  
  /.../m9tn/lib/python2.7/site-packages/pandas/io/parsers.pyc in _make_engine(self, engine)
      703     def _make_engine(self, engine='c'):
      704         if engine == 'c':
  --&gt; 705             self._engine = CParserWrapper(self.f, **self.options)
      706         else:
      707             if engine == 'python':
  
  /.../lib/python2.7/site-packages/pandas/io/parsers.pyc in __init__(self, src, **kwds)
     1070         kwds['allow_leading_cols'] = self.index_col is not False
     1071 
  -&gt; 1072         self._reader = _parser.TextReader(src, **kwds)
     1073 
     1074         # XXX
  
  pandas/parser.pyx in pandas.parser.TextReader.__cinit__ (pandas/parser.c:4732)()
  
  pandas/parser.pyx in pandas.parser.TextReader._get_header (pandas/parser.c:7330)()
  
  ValueError: Passed header names mismatches usecols
  </code></pre>