#!usr/bin/env python3
import os
import sys
import base64
import urllib.request
import shutil

def checkEnv(name, strict=False):
    if not name in os.environ or os.environ[name] == '':
        if strict:
            print('Error need env var \'%s\'' % (name))
            sys.exit(22)
        return False
    return os.environ[name]

def download(url, dest, headers):
    req = urllib.request.Request(url)
    for header in headers:
        req.add_header(header, headers[header])
    with urllib.request.urlopen(req) as response, \
        open(dest, 'wb') as out_file:
        shutil.copyfileobj(response, out_file)

def main():
    username = 'AUTH_USER'
    username = checkEnv(username, strict=True)
    password = 'AUTH_PASS'
    password = checkEnv(password, strict=True)
    url = 'URL'
    url = checkEnv(url, strict=True)
    dest = 'DEST'
    dest = checkEnv(dest, strict=True)

    concat = username + ":" + password
    concat = concat.encode('utf8')
    download(url, dest, {
        'Autorization': 'Basic %s' % (base64.b64encode(concat))
    })

if __name__ == '__main__':
    main()