title: robot framework: exception handling
body: <p>Is it possible to handle exceptions from the test case?  I have 2 kinds of failure I want to track: a test failed to run, and a test ran but received the wrong output. If I need to raise an exception to fail my test, how can I distinguish between the two failure types? So say I have the following:</p>
  
  <pre><code>*** Test Cases ***
  Case 1
      Login            1.2.3.4    user    pass
      Check Log For    this log line
  </code></pre>
  
  <p>If I can't log in, then the <code>Login</code> Keyword would raise an <code>ExecutionError</code>. If the log file doesn't exist, I would also get an <code>ExecutionError</code>. But if the log file does exist and the line isn't in the log, I should get an <code>OutputError</code>.</p>
  
  <p>I may want to immediately fail the test on an <code>ExecutionError</code>, since it means my test did not run and there is some issue that needs to be fixed in the environment or with the test case.  But on an <code>OutputError</code>, I may want to continue the test. It may only refer to a single piece of output and the test may be valuable to continue to check the rest of the output.</p>
  
  <p>How can this be done?</p>