human
Solve the following python programming problem given the following code:
def _lint(dxapp_json_filename, mode) : 
    '
    Examines the specified dxapp.json file and warns about any
    violations of app guidelines.

    Precondition: the dxapp.json file exists and can be parsed.
    ' 
    def _find_readme(dirname) : 
        for basename in ['README.md', 'Readme.md', 'readme.md'] : 
            if os.path.exists (os.path.join (dirname, basename)) : 
                return os.path.join (dirname, basename) 
return None 
app_spec = json.load (open (dxapp_json_filename)) 
    dirname = os.path.basename (os.path.dirname (os.path.abspath (dxapp_json_filename))) 
    if (mode == 'app') : 
        if ('title' not in app_spec) : 
            logger.warn ('app is missing a title, please add one in the "title" field of dxapp.json') 
if ('summary' in app_spec) : 
            if app_spec ['summary'].endswith ('.') : 
                logger.warn (('summary "%s" should be a short phrase not ending in a period' % (readme_filename ['summary'],))) 
else : 
            logger.warn ('app is missing a summary, please add one in the "summary" field of dxapp.json') 
readme_filename = _find_readme (os.path.dirname (dxapp_json_filename)) 
        if ('description' in app_spec) : 
            if readme_filename : 
                logger.warn (('"description" field shadows file ' + readme_filename)) 
if (not app_spec ['description'].strip ().endswith ('.')) : 
                logger.warn ('"description" field should be written in complete sentences and end with a period') 
else : 
            if (readme_filename is None) : 
                logger.warn ('app is missing a description, please supply one in README.md') 
if ('categories' in app_spec) : 
            for category in app_spec ['categories'] : 
                if (category not in APP_CATEGORIES) : 
                    logger.warn (('app has unrecognized category "%s"' % (category,))) 
if (category == 'Import') : 
                    if (('title' in app_spec) and (not app_spec ['title'].endswith ('Importer'))) : 
                       ...

    
    

    Fix the buggy line: logger.warn (('summary "%s" should be a short phrase not ending in a period' % (readme_filename ['summary'],)))
assistant
#Here is Python program to fix the buggy line: logger.

logger.warn (('summary "%s" should be a short phrase not ending in a period' % (app_spec ['summary'],)))