Show login instead of 404 on credit-card for anon

I'd like to link directly to the /credit-card.html page when publicizing
that we're back w/ credit card acceptance, but I don't want folks who
are unauthenticated to get a gnarly 404. #58

www/credit-card.html

@@ -5,31 +5,42 @@
 from gittip import billing
 
 # ========================================================================== ^L
-if user.ANON:
- raise Response(404)
-
-stripe_customer_id = user.stripe_customer_id
-if not stripe_customer_id:
- status = "missing"
-else:
- working = not bool(user.last_bill_result)
- status = "working" if working else "failing"
-
-try:
- customer = billing.Customer(stripe_customer_id)
-except: # stripe is unavailable? could be a bad stripe_customer_id?
- log(traceback.format_exc())
- stripe_down = True
-else:
- assert stripe_customer_id == customer['id']
- stripe_down = False
-
-username = user.id
+
+if not user.ANON:
+ stripe_customer_id = user.stripe_customer_id
+ if not stripe_customer_id:
+ status = "missing"
+ else:
+ working = not bool(user.last_bill_result)
+ status = "working" if working else "failing"
+
+ try:
+ customer = billing.Customer(stripe_customer_id)
+ except: # stripe is unavailable? could be a bad stripe_customer_id?
+ log(traceback.format_exc())
+ stripe_down = True
+ else:
+ assert stripe_customer_id == customer['id']
+ stripe_down = False
+
+ username = user.id
 # ========================================================================== ^L
 {% extends templates/base.html %}
 
 
 {% block body %}
+{% if user.ANON %}
+<div id="their-voice">
+
+<h2 class="first">Credit Card</h2>
+
+<p>Sign in <a href="{{ github_oauth_url('/credit-card.html') }}">with
+GitHub</a>, and then you&rsquo;ll be able to add or change your credit card.
+Thanks! :-)</p>
+
+</div>
+
+{% else %}
 <script>
  $(document).ready(function()
  {
@@ -163,3 +174,4 @@ <h2>Delete credit card.</h2>
 
 </div>
 {% end %}
+{% end %}

www/github/associate

@@ -47,12 +47,15 @@ log("Done with OAuth dance with Github for %s (%s)."
 
 # Bind to a participant.
 # ======================
-# Redirect to the new participant, or to the one they came from.
+# Redirect to the new participant, or to the one they came from, or wherever 
+# else they came from.
 
 participant_id = github.upsert(user_info, claim=True)
 user = User.from_id(participant_id)
 then = qs.get('then')
 if then is not None:
+ if then.startswith('/'):
+ request.redirect(then)
  participant_id = 'github/' + then
 request.redirect('/%s/' % participant_id)