title: Distributed 1.21.8 requires msgpack, which is not installed
body: <p>I'm having a problem trying to install plotly. I proceeded to upgrade anaconda using the command line on Debian 9 and I received the error message "distributed 1.21.0 requires msgpack, which is not installed". </p>
  
  <p>Then I tried a <code>conda install mspack</code>, then a <code>pip install --upgade plotly</code>, and I get "distributed 1.22.0 requires msgpack, which is not installed". This 1.22.0 error message is what kicked off my whole upgrading process of many packages. Does this break plotly? Don't know, haven't tried but judging from msgpack website <a href="https://msgpack.org/" rel="noreferrer">https://msgpack.org/</a>, it is probable to cause errors. We'll see, I guess. Not sure what else to do. </p>
  
  <p><code>pip install msgpack</code> does not fix the problem </p>