Read excell file with python, validate and return defaultdict

import os
import xlrd
from collections import defaultdict
import sys
from pprint import pprint
import re

'''
Some name1     2345        someemal1@gmail.com
Some name12    23456        someemal2@gmail.com
Some name1    0            someemal1@gmail.com
Some name3    0889345        someemal1@gmail.com
'''

filename = "somefile.xls"
result = defaultdict(list)


def checkFilename(filename):
    '''Check file is excel or not '''
    if filename.endswith('xls'):
        return filename
    else:
        return 'Not valid filename'
        sys.exit()


class ReadXLS:

    def __init__(self, checkFilename):
        self.filename = checkFilename

    def realReadFilename(self):
        '''Read xls file with xlrd module '''
        try:
            workbook = xlrd.open_workbook(self.filename)
        except:
            print("some error...")
            sys.exit()
        else:
            try:
                sheet = workbook.sheet_by_index(0)
            except IndexError as ie:
                print(ie)
                sys.exit()
            else:
                for rowx in range(sheet.nrows):
                    columnmapping = sheet.row_values(rowx)
                    yield columnmapping

    def checkResult(self):
        '''add to result only what i whant'''
        for line in ReadXLS.realReadFilename(self):
            if ((line[0] in (None, '')) or (line[1] in (None, ''))
                    or (line[2] in (None, '')) or not
                    re.search(r'[\w.-]+@[\w.-]+.\w+', line[2])):
                continue
            else:
                #result[line[2].upper()].append((line[0], line[1]))
                result[line[2].upper()].append(
                    (line[1].strip().replace(' ', ''), line[0].strip())
                )

    def __repr__(self):
        ''' Why I can '''
        return "{}".format(self.filename)


if __name__ == '__main__':
    test = ReadXLS(checkFilename(filename))
    test.checkResult()
    pprint(result)