title: KeyError(f"None of [{key}] are in the [{axis_name}]") after upgrading from python 3.6 to 3.8
body: <p>I just moved to a new MacBook Pro, installed python 3.8 and pip installed the packages I had in old MBP. I was running python 3.6 in old MBP. I am now getting an error in a python script and I believe the only difference is python 3.8 (instead of python 3.6)</p>
  <p>error is ...  <strong>KeyError(f&quot;None of [{key}] are in the [{axis_name}]&quot;)</strong></p>
  <p>The last line in code below to define the plot is the one that is being called out for the error. Attached screenshot shows the output of the print statements and the error.</p>
  <p>Any help is appreciated as I'm running into a wall now. TIA.</p>
  <pre><code>print(&quot;Index&quot;)
  print(df_transpose_deaths.index)
  
  print(&quot;Columns&quot;)
  print(df_transpose_deaths.columns)
  
  print(&quot;df transpose deaths&quot;)
  print(df_transpose_deaths)
  
  xindex = df_transpose_deaths.index
  ycolumns = df_transpose_deaths.columns
  deaths_world_plot = df_transpose_deaths.plot(x = xindex, y = ycolumns, kind='line', xticks=x_ticks, legend=False)
  </code></pre>
  <p><a href="https://i.stack.imgur.com/APWU8.jpg" rel="nofollow noreferrer">screenshot of terminal window with error message</a></p>