Program to read emails in python using imaplib

I write a python script to read the emails but it is not working.I am getting library errors. I enabled imap and pop in email. currently i am using ubuntu os . I tried to run this script using python and python3 both but still i am getting these errors.

import imaplib
import base64
email_user = input('Email: ')
email_pass = input('Password: ')

M = imaplib.IMAP4_SSL('imap.gmail',993)
M.login(email_user, email_pass)
M.select()

typ, message_numbers = M.search(None, 'ALL')  # change variable name, and use new name in for loop

for num in message_numbers[0].split():
    typ, data = M.fetch(num, 'RFC822')
    num1 = base64.b64decode(num)          # unnecessary, I think
    print(data)   # check what you've actually got. That will help with the next line
    data1 = base64.b64decode(data[0][1])
    print('Message %s\n%s\n' % (num, data1))

M.close()
M.logout()

i am getting these errors

Traceback (most recent call last):
  File "imapgit.py", line 6, in <module>
    M = imaplib.IMAP4_SSL('imap.gmail',993)
  File "/usr/lib/python3.6/imaplib.py", line 1288, in __init__
    IMAP4.__init__(self, host, port)
  File "/usr/lib/python3.6/imaplib.py", line 198, in __init__
    self.open(host, port)
  File "/usr/lib/python3.6/imaplib.py", line 1301, in open
    IMAP4.open(self, host, port)
  File "/usr/lib/python3.6/imaplib.py", line 299, in open
    self.sock = self._create_socket()
  File "/usr/lib/python3.6/imaplib.py", line 1291, in _create_socket
    sock = IMAP4._create_socket(self)
  File "/usr/lib/python3.6/imaplib.py", line 289, in _create_socket
    return socket.create_connection((host, self.port))
  File "/usr/lib/python3.6/socket.py", line 704, in create_connection
    for res in getaddrinfo(host, port, 0, SOCK_STREAM):
  File "/usr/lib/python3.6/socket.py", line 745, in getaddrinfo
    for res in _socket.getaddrinfo(host, port, family, type, proto, flags):
socket.gaierror: [Errno -2] Name or service not known