Issue webcompat#3204 - Modifies /api/issues to handle error

Our function needs probably to be refactored so that
it becomes easier to test. See previous commit.

webcompat/api/endpoints.py

@@ -16,6 +16,7 @@
 from flask import Blueprint
 from flask import g
 from flask import request
+from flask import Response
 from flask import session
 
 from webcompat import app
@@ -84,7 +85,7 @@ def proxy_issues():
     # Non-authed users should never get here--the request is made to
     # GitHub client-side)--but return out of paranoia anyways.
     elif params.get('q'):
-        abort(404)
+        abort(Response('Nope', status=404, content_type='text/plain'))
     path = 'repos/{0}'.format(ISSUES_PATH)
     return api_request('get', path, params=params)