Add some rudimentary error checking to forum views

[Hopefully fix #34992235]

lms/djangoapps/django_comment_client/forum/views.py

 from django.contrib.auth.decorators import login_required
 from django.views.decorators.http import require_POST
-from django.http import HttpResponse
+from django.http import HttpResponse, Http404
 from django.utils import simplejson
 from django.core.context_processors import csrf
 from django.core.urlresolvers import reverse
@@ -98,6 +98,10 @@ def render_user_discussion(*args, **kwargs):
     return render_discussion(discussion_type='user', *args, **kwargs)
 
 def get_threads(request, course_id, discussion_id=None):
+    """
+    This may raise cc.utils.CommentClientError or
+    cc.utils.CommentClientUnknownError if something goes wrong.
+    """
 
     default_query_params = {
         'page': 1,
@@ -122,7 +126,14 @@ def get_threads(request, course_id, discussion_id=None):
 
 # discussion per page is fixed for now
 def inline_discussion(request, course_id, discussion_id):
+    try:
         threads, query_params = get_threads(request, course_id, discussion_id)
+    except (cc.utils.CommentClientError, cc.utils.CommentClientUnknownError) as err:
+        # TODO (vshnayder): since none of this code seems to be aware of the fact that
+        # sometimes things go wrong, I suspect that the js client is also not
+        # checking for errors on request.  Check and fix as needed.
+        raise Http404
+
     html = render_inline_discussion(request, course_id, threads, discussion_id=discussion_id,  \
                                                                  query_params=query_params)
 
@@ -143,6 +154,7 @@ def render_search_bar(request, course_id, discussion_id=None, text=''):
 
 def forum_form_discussion(request, course_id):
     course = get_course_with_access(request.user, course_id, 'load')
+    try:
         threads, query_params = get_threads(request, course_id)
         content = render_forum_discussion(request, course_id, threads, discussion_id=_general_discussion_id(course_id), query_params=query_params)
 
@@ -171,6 +183,9 @@ def forum_form_discussion(request, course_id):
             }
             # print "start rendering.."
             return render_to_response('discussion/index.html', context)
+    except (cc.utils.CommentClientError, cc.utils.CommentClientUnknownError) as err:
+        raise Http404
+
 
 def render_single_thread(request, discussion_id, course_id, thread_id):
 
@@ -192,6 +207,7 @@ def render_single_thread(request, discussion_id, course_id, thread_id):
 
 def single_thread(request, course_id, discussion_id, thread_id):
 
+    try:
         if request.is_ajax():
 
             user_info = cc.User.from_django_user(request.user).to_dict()
@@ -231,10 +247,13 @@ def single_thread(request, course_id, discussion_id, thread_id):
             }
 
             return render_to_response('discussion/single_thread.html', context)
+    except (cc.utils.CommentClientError, cc.utils.CommentClientUnknownError) as err:
+        raise Http404
 
 def user_profile(request, course_id, user_id):
 
     course = get_course_with_access(request.user, course_id, 'load')
+    try:
         profiled_user = cc.User(id=user_id, course_id=course_id)
 
         query_params = {
@@ -264,3 +283,5 @@ def user_profile(request, course_id, user_id):
             }
 
             return render_to_response('discussion/user_profile.html', context)
+    except (cc.utils.CommentClientError, cc.utils.CommentClientUnknownError) as err:
+        raise Http404

lms/lib/comment_client/utils.py

-import requests
 import json
+import logging
+import requests
 import settings
 
+log = logging.getLogger('mitx.' + __name__)
+
 def strip_none(dic):
     return dict([(k, v) for k, v in dic.iteritems() if v is not None])
 
@@ -23,10 +26,17 @@ def perform_request(method, url, data_or_params=None, *args, **kwargs):
     if data_or_params is None:
         data_or_params = {}
     data_or_params['api_key'] = settings.API_KEY
+    try:
         if method in ['post', 'put', 'patch']:
             response = requests.request(method, url, data=data_or_params)
         else:
             response = requests.request(method, url, params=data_or_params)
+    except Exception as err:
+        log.exception("Trying to call {method} on {url} with params {params}".format(
+            method=method, url=url, params=data_or_params))
+        # Reraise with a single exception type 
+        raise CommentClientError(str(err))
+
     if 200 < response.status_code < 500:
         raise CommentClientError(response.text)
     elif response.status_code == 500: