Investigate proxy authentication issues in simplenote.vim. See https://github.com/i5m/simplenote.vim/commit/8d0a0d9a1d7c8edee3efc28cef62936f36b2b4d4

gistfile1.py

import urllib
import urllib2
import base64
import json

snuser = ""
snpassword = ""
proxyurl = "<proxy url>:<proxy port>"
proxylogin = "<proxy username>:<proxy password>"

#Fetch Simplenote token
auth_params = "email=%s&password=%s" % (urllib2.quote(snuser), urllib2.quote(snpassword))
values = base64.encodestring(auth_params)
AUTH_URL = 'https://simple-note.appspot.com/api/login'

request = urllib2.Request(AUTH_URL, values)

#Behind a proxy
res = urllib2.urlopen(request).read()
#Will fail as expected

#Set proxy authentication
request.set_proxy(proxyurl, 'http')
request.add_header('Proxy-Authorization', 'Basic %s' % base64.b64encode(proxylogin))

#This then works
res = urllib2.urlopen(request).read()

#Now fetch a list of notes
token = res
INDX_URL = 'https://simple-note.appspot.com/api2/index?'
params = 'auth=%s&email=%s&length=%s' % (token, urllib2.quote(snuser), 20)

request = urllib2.Request(INDX_URL+params)
request.set_proxy(proxyurl, 'http')
request.add_header('Proxy-Authorization', 'Basic %s' % base64.b64encode(proxylogin))
res = json.loads(urllib2.urlopen(request).read())

#This works. Why the hell doesn't it work in Simplenote.vim?
#Actually, after further testing this seems to only sporadically work. Perhaps there are issues with the API and/or my proxy?

#Sometimes doing this helps, sometimes not:
request.set_proxy(proxyurl, 'https')
request.set_proxy(proxyurl, 'http')