title: Openpyxl - WinError 32 while trying to save workbook after formatting applied
body: <p>I am unable to save workbooks when I apply formatting to a worksheet (for example, setting row_dimensions to an integer, or column dimensions to an integer).</p>
  
  <p>Code snippet:</p>
  
  <pre><code>import openpyxl
  
  wb = openpyxl.Workbook()
  ws = wb.active
  ws['A1'].value = 'test'
  ws.row_dimensions[1] = 10
  wb.save('example.xlsx')
  </code></pre>
  
  <p>Traceback info:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;&gt;", line 7, in &lt;module&gt;
      wb.save('practicewb')
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\workbook\workbook.py", line 409, in save
      save_workbook(self, filename)
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\writer\excel.py", line 294, in save_workbook
      writer.save()
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\writer\excel.py", line 276, in save
      self.write_data()
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\writer\excel.py", line 76, in write_data
      self._write_worksheets()
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\writer\excel.py", line 216, in _write_worksheets
      self.write_worksheet(ws)
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\writer\excel.py", line 201, in write_worksheet
      writer.write()
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\worksheet\_writer.py", line 356, in write
      self.write_rows()
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\worksheet\_writer.py", line 124, in write_rows
      self.write_row(xf, row, row_idx)
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\worksheet\_writer.py", line 133, in write_row
      attrs.update(dims.get(row_idx, {}))
  TypeError: 'int' object is not iterable
  Error in atexit._run_exitfuncs:
  Traceback (most recent call last):
    File "C:\Program Files (x86)\Python37-32\lib\site-packages\openpyxl\worksheet\_writer.py", line 33, in _openpyxl_shutdown
      os.remove(path)
  PermissionError: [WinError 32] The process cannot access the file because it is being used by another process: 'C:\\Users\\philt\\AppData\\Local\\Temp\\openpyxl.gtzivgcp'
  
  Process finished with exit code 1
  </code></pre>
  
  <p>I do not have any folders or programs open that are using the workbook, aside from openpyxl itself.</p>
  
  <p>What could be the problem here?</p>
  
  <p>Thank you!</p>