title: CondaValueError: The target prefix is the base prefix. Aborting
body: <p>I have the following conda environment file <code>environment.yml</code>:</p>
  
  <pre><code>name: testproject
  channels:
  - defaults
  dependencies:
  - python=3.7
  prefix: /opt/projects/testproject
  </code></pre>
  
  <p>Before creating the environment, only the base environment exists:</p>
  
  <pre><code>(base) me@mymachine:/opt/projects/testproject$ conda env list
  # conda environments:
  #
  base                  *  /opt/anaconda/anaconda3
  </code></pre>
  
  <p>When trying to create the environment, I get the following error:</p>
  
  <pre><code>(base) me@mymachine:/opt/projects/testproject$ conda create -f environment.yml
  
  CondaValueError: The target prefix is the base prefix. Aborting.
  </code></pre>
  
  <p>What does this error mean?</p>