title: conda uninstall quits without removing anything
body: <p>I've tried to remove packages using conda uninstall.  The command runs for a long time, takes up a large amount of memory (but doesn't run out I believe) and then quits with no indication of having completed the 'Solving environment' step.  When I check, the package is still there.  For example:</p>
  <pre><code>(base) pm@pm:~/Software/anaconda3/bin$ conda uninstall -n base pytorch
  Collecting package metadata (repodata.json): done
  Solving environment: - (base) pm@pm:~/Software/anaconda3/bin$ conda list -n base -f pytorch
  # packages in environment at /home/pm/Software/anaconda3:
  #
  # Name                    Version                   Build  Channel
  pytorch                   1.7.1           py3.7_cuda10.1.243_cudnn7.6.3_0    pytorch
  </code></pre>
  <p>I've also tried remove, which does exactly the same thing.  Suggestions welcome!</p>