title: IndexError: At least one sheet must be visible
body: <pre><code> def multiple_dfs(sheet, row=2):
  
      writer = pd.ExcelWriter("testing.xlsx", engine='openpyxl')
  
      f1 = {
          'user': ['Bob', 'Jane', 'Alice'], 
          'income': [40000, 50000, 42000],
      }
  
      f2 = {
          'amount': ['Chest', 'Bras', 'Braa'], 
          'income': [40000, 50000, 42000]
      }
  
      frames = [f1, f2]
  
  
      for f in frames:
          try:
              wb = load_workbook("testing.xlsx")
              ws = wb.get_sheet_by_name("aaa")
  
              writer.wb = wb
              writer.sheets = dict((ws.title, ws) for ws in wb.worksheets)
  
              row = ws.max_row + 2
          except:
              pass 
  
          df = pd.DataFrame(f)
          df.to_excel(writer, sheet, startrow=row, index=False)
          writer.save()
      # writer.close()
  
  multiple_dfs('aaa')
  </code></pre>
  
  <p>I got this error, but I can't fix it. I adapt this short representation of what is happening in my code, but it is hard to see where is the real problem. Here is the </p>
  
  <pre><code>Traceback (most recent call last):
    File "create_and_update_xlsx_sheets.py", line 144, in &lt;module&gt;
      create_and_update_worksheets()
    File "create_and_update_xlsx_sheets.py", line 140, in create_and_update_worksheets
      writer.save()
    File "/home/jeremie/.virtualenvs/NHL/lib/python3.5/site-packages/pandas/io/excel.py", line 824, in save
      return self.book.save(self.path)
    ...
    File "/home/jeremie/.virtualenvs/NHL/lib/python3.5/site-packages/openpyxl/writer/workbook.py", line 61, in get_active_sheet
      raise IndexError("At least one sheet must be visible")
  IndexError: At least one sheet must be visible
  </code></pre>
  
  <p>How could I fix that issue?</p>
  
  <p><strong>P.S.</strong> Be aware that error is displayed half the time.</p>