NameError: name 'FileNotFoundError' is not defined

可能是python版本的问题

详情参见如下

#py2.7
filename='waiwai.txt'
try:
    with open(filename) as f_obj:
        contents=f_obj.read()
except FileNotFoundError:
    print "Sorry,the file does't exist."

#py3.7
filename='waiwai.txt'
try:
    with open(filename) as f_obj:
        contents=f_obj.read()
except IOError:
    print "Sorry,the file does't exist."