Configures the xunit plugin.

def configure(self, options, config):
        """Configures the xunit plugin."""
        Plugin.configure(self, options, config)
        self.config = config
        if self.enabled:
            self.jinja = Environment(
                loader=FileSystemLoader(os.path.join(os.path.dirname(__file__), 'templates')),
                trim_blocks=True,
                lstrip_blocks=True
            )
            self.stats = {'errors': 0, 'failures': 0, 'passes': 0, 'skipped': 0}
            self.report_data = defaultdict(Group)
            self.report_file = codecs.open(options.html_file, 'w', self.encoding, 'replace')