title: UnboundLocalError: local variable 'arith_flex' referenced before assignment
body: <p>I was teaching a workshop today, and 5 people in my class had the error mentioned above when they used the line <code>import pandas as pd</code>.</p>
  
  <p>Here's the traceback:</p>
  
  <p><a href="https://i.stack.imgur.com/Hw7m3.png" rel="noreferrer"><img src="https://i.stack.imgur.com/Hw7m3.png" alt="enter image description here"></a></p>
  
  <p>I've never heard of this variable before, and there was no mention of this particular issue with pandas in this particular context.</p>
  
  <p>Some background:</p>
  
  <ul>
  <li>These people were on corporate computers, so there may have been permissions denied to them on their own computer</li>
  <li>They couldn't get regular Anaconda Navigator working, so they were using miniconda</li>
  <li>This error message showed up when they tried to import pandas and seaborn, but not matplotlib or sklearn</li>
  <li>they had done the install a week before, and no one mentioned having touched the software in the meantime</li>
  <li>this simulaltaneously happened on 5 different people's computers</li>
  </ul>
  
  <p>Any idea what the issue may have been?</p>