import requests

def check_links(args_obj, parser):
    print("")
    print("Checking links")
    print("########################")
    print("Not implemented yet.")
    print("This is supposed to check all links in the system.")
    print("########################")

from __future__ import print_function
import re
import requests
from lxml.html import parse
from requests.exceptions import ConnectionError

def is_root_link(link):
    pattern = re.compile("^/$")
    return pattern.match(link)

def is_mailto_link(link):
    pattern = re.compile("^mailto:.*")
    return pattern.match(link)

def is_internal_link(link):
    pattern = re.compile("^/.*")
    return pattern.match(link)

def get_links(doc):
    return filter(
        lambda x: not (
            is_root_link(x)
            or is_mailto_link(x))
        , map(lambda y: y.get("href")
              , doc.cssselect("a")))

def verify_link(link):
    try:
        result = requests.get(link, timeout=20)
        if result.status_code == 200:
            print(link+" ==> OK")
        else:
            print("ERROR: link `"+link+"` failed with status "
                  , result.status_code)
    except ConnectionError as ex:
        print("ERROR: ", link, ex)

def check_page(host, start_url):
    print("")
    print("Checking links in page `"+start_url+"`")
    doc = parse(start_url).getroot()
    links = get_links(doc)
    internal_links = filter(is_internal_link, links)
    external_links = filter(lambda x: not is_internal_link(x), links)
    external_links.append("http://somenon-existentsite.brr")
    for link in internal_links:
        verify_link(host+link)

    for link in external_links:
        verify_link(link)

def check_links(args_obj, parser):
    print("")
    print("Checking links")
    host = args_obj.host

    # Check the home page
    check_page(host, host)

    # Check traits page
    check_page(
        host,
        host+"/show_trait?trait_id=1435395_s_at&dataset=HC_M2_0606_P")

Add tests to check links.