title: Exception calling "Remove" with "0" argument(s): "The given key was not present in the dictionary
body: <p>I have added a migration using <code>Add-Migration</code>, Now If I run <code>Remove-Migration</code>, it reverts the migration and remove the generated migration file successfully, but gives the error in Package Manager Console also. I could not figure out the exact reason behind it and side effect of it. Is this EF Core bug?</p>
  
  <p><strong>Package Manager Output:</strong></p>
  
  <blockquote>
    <p>PM> Remove-Migration Removing migration
    '20180320052521_testMigration'. Reverting model snapshot. Done.
    Exception calling "Remove" with "0" argument(s): "The given key was
    not present in the dictionary." PM></p>
  </blockquote>
  
  <p><strong>EF Core Version:</strong> 2.0.1</p>