title: TypeError when trying to open a workbook using openpyxl
body: <p>I'm trying to use openpyxl to open and modify an existing excel workbook, but I can't even open the file without getting an error.</p>
  
  <pre><code>from openpyxl import load_workbook
  ws = load_workbook('PO-Copy.xlsx')
  </code></pre>
  
  <p>I get a long TypeError as a result:</p>
  
  <pre><code>Traceback (most recent call last):
  File "&lt;module1&gt;", line 6, in &lt;module&gt;
  File "C:\Python27\Lib\site-packages\openpyxl\reader\excel.py", line 151, in load_workbook
       _load_workbook(wb, archive, filename, read_only, keep_vba)
  File "C:\Python27\Lib\site-packages\openpyxl\reader\excel.py", line 224, in _load_workbook
        keep_vba=keep_vba)
  File "C:\Python27\Lib\site-packages\openpyxl\reader\worksheet.py", line 308, in read_worksheet
       fast_parse(ws, xml_source, shared_strings, style_table, color_index)
  File "C:\Python27\Lib\site-packages\openpyxl\reader\worksheet.py", line 296, in fast_parse
       parser.parse()
  File "C:\Python27\Lib\site-packages\openpyxl\reader\worksheet.py", line 84, in parse
       dispatcher[tag_name](element)
  File "C:\Python27\Lib\site-packages\openpyxl\reader\worksheet.py", line 282, in parse_data_validation
       dv = parser(tag)
  File "C:\Python27\Lib\site-packages\openpyxl\worksheet\datavalidation.py", line 179, in parser
       dv = DataValidation(**element.attrib)
  TypeError: __init__() got an unexpected keyword argument 'errorStyle'
  </code></pre>
  
  <p>Has anyone else ran into this error?  is there a fix I can use to keep going?</p>