title: Openpyxl iterating through cells, can't compare cells to string
body: <p>I am having issues iterating through every cell in a workbook and comparing the call's value to a string object.  I am able to successfully compare to datetime objects in the workbook but when it comes to regular 'String' objects nothing is being printed, and the cells are not updating.</p>
  
  <pre><code>wb = openpyxl.load_workbook(pathz, read_only=False)
  ws = wb.active
      for row in ws.iter_rows():
          for cell in row:
              if cell.value == a:
                  print("Found datetime cell")
                  cell.value = newDate
  
              if cell.value == "Hello":
                  print("Found string cell")
                  cell.value = "Goodbye"
  
  wb.save(pathz)
  </code></pre>