human
Solve the following python programming problem given the following code:
def __call__(self, environ, start_response) : 
    state = { 
        
} 
    def replacement_start_response(status, headers, exc_info = None) : 
        'Overrides the default response to make errors parsable.' 
        try : 
            status_code = int (status.split (' ') [0]) 
            state ['status_code'] = status_code 
except (ValueError, TypeError) : 
            raise Exception ((_ ('ErrorDocumentMiddleware received an invalid status %s') % status)) 
else : 
            if ((state ['status_code'] // 100) not in (2, 3)) : 
                headers = [(h, v) for (h, v) in headers if (h not in ('Content-Length', 'Content-Type'))] 
state ['headers'] = headers 
            return start_response (status, headers, exc_info) 
app_iter = self.app (environ, replacement_start_response) 
    if ((state ['status_code'] // 100) not in (2, 3)) : 
        req = webob.Request (environ) 
        if (req.accept.best_match (['application/json', 'application/xml']) == 'application/xml') : 
            try : 
                body = [et.ElementTree.tostring (et.ElementTree.fromstring ((('<error_message>' + '
'.join (app_iter)) + '</error_message>')))] 
except et.ElementTree.ParseError as err : 
                LOG.error (_LE ('Error parsing HTTP response: %s'), err) 
                body = [(('<error_message>%s' % state ['status_code']) + '</error_message>')] 
state ['headers'].append (('Content-Type', 'application/xml')) 
else : 
            if six.PY3 : 
                app_iter = [i.decode ('utf-8') for i in app_iter] 
body = [json.dumps ({ 
                'error_message' : '
'.join (item), 
})] 
            if six.PY3 : 
                body = [item.encode ('utf-8') for item in body] 
state ['headers'].append (('Content-Type', 'application/json')) 
state ['headers'].append (('Content-Length', str (len (body [0])))) 
else : 
        body = app_iter 
return body 

    
    

    Fix the buggy line: 'error_message' : '
'.join (item) ,
assistant
#Here is Python program to fix the buggy line: 'error_message' : '
.

'error_message' : '
'.join (app_iter) ,