title: How do I check if an environment variable exists in Robot?
body: <p><code>Variable Should Exist</code> does not work with environment variables, when I try it throws this error <code>Invalid variable syntax '%{ENV_VAR}'</code>.</p>
  
  <p>Is there a way to check without assigning the value of the env_var to a local var and use the keyword above on that?</p>