title: Error message when using openpyxl.load_workbook() function
body: <p>I have just started to learn programming and I am currently trying to read an excel file from IDLE. I'm following instruction from the book "Automate the Boring Stuff". I have successfully imported openpyxl, and thereafter, as instructed tried <code>wb = openpyxl.load_workbook('example.xlsx')</code> where I exchanged "example" to the actual name of the workbook. However, I get this error message: </p>
  
  <pre><code>Traceback (most recent call last):   File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/openpyxl/reader/excel.py", line 117, in load_workbook
      archive = ZipFile(filename, 'r', ZIP_DEFLATED)   File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/zipfile.py", line 1216, in __init__
      self.fp = io.open(file, filemode) FileNotFoundError: [Errno 2] No such file or directory: 'jan.xlsx'
  </code></pre>
  
  <p>During handling of the above exception, another exception occurred:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;pyshell#4&gt;", line 1, in &lt;module&gt;
      wb = openpyxl.load_workbook('jan.xlsx')
    File "/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/site-packages/openpyxl/reader/excel.py", line 145, in load_workbook
      raise InvalidFileException(unicode(e))
  openpyxl.exceptions.InvalidFileException: [Errno 2] No such file or directory: 'jan.xlsx' 
  </code></pre>
  
  <p>I don't understand how to solve this.</p>