It looks like some servers using basic authentication don't include quotes around the realm (example https://api.connect2field.com) as required by rfc 2617. urllib wont handle these requests and silently fails, but a simple change to the regex in AbstractBasicAuthHandler from
 
'realm=(["\'])(.*?)\\2', re.I)
to
'realm=(["\']?)(["\']*)\\2', re.I)

would make authentication more flexible.