Try different encoding to open a file in readonly mode

def readFile(cls, filepath):
        """Try different encoding to open a file in readonly mode"""
        for mode in ("utf-8", 'gbk', 'cp1252', 'windows-1252', 'latin-1'):
            try:
                with open(filepath, mode='r', encoding=mode) as f:
                    content = f.read()
                    cit.info('以 {} 格式打开文件'.format(mode))
                    return content
            except UnicodeDecodeError:
                cit.warn('打开文件：尝试 {} 格式失败'.format(mode))
        return None