title: Want to filter out failure Message from my robot framework output files
body: <p>I want to filter failure messages from output files generated after executing my testcases in Robot Framework. I have tried modules like from <strong>robot.api import ExecutionResult</strong> but it gives me only only count of Passed and Failed Testcases.</p>
  
  <p>I have also tried other Robot framework Libtraries like <strong>import robot.errors</strong> to filter out all error messages but didn't get any luck. Below is my code block:
  `</p>
  
  <pre><code>#!/usr/bin/python
  from robot.api import ExecutionResult
  import robot.errors
  from robot.result.visitor import ResultVisitor
  xmlpath = "&lt;output.xml PATH&gt;"
  result = ExecutionResult(xmlpath)
  result.configure(stat_config={'suite_stat_level': 2,
                                'tag_stat_combine': 'tagANDanother'})
  stats = result.statistics
  print stats.total.critical.failed
  print stats.total.critical.passed
  print stats.total.critical.passed + stats.total.critical.failed
  
  class FailureCollector(ResultVisitor):
      def __init__(self):
          self.failures = []
  
      def visit_test(self, test):
          if not test.passed:
          self.failures += [test]
  
  failure_collector = FailureCollector()
  result.visit(failure_collector)
  print failure_collector.failures
  #the above print gives me all failed testcases as a list Eg: ['test1:My example Testcase1','test2:My example Testcase2' ]`
  </code></pre>
  
  <p>Any example to get this work done will be very helpful.</p>