urllib urlopen getting error 400 on 1 specific page

[snippsat]

Use Requests not urllib.

>>> import requests
>>> my_url = 'http://www.nasdaqomxnordic.com/aktier'
>>> r = requests.get(my_url)
>>> r.status_code
200

Basic getting title.

import requests
from bs4 import BeautifulSoup

url = 'http://www.nasdaqomxnordic.com/aktier'
url_get = requests.get(url)
soup = BeautifulSoup(url_get.content, 'lxml')
print(soup.find('title').text)

Output:
Shares - share prices for all companies listed on NASDAQ OMX Nordic  - Nasdaq

Sites like this us a lot of JavaScripts,so look if there is a API that eg give JSON back.
Plain scraping so may you need Selenium to get JavaScripts content.