Attempt to debug SSL cert validation error

This changeset introduces a few changes:

* Removes UK Notify Logo URL and config
* Removes UK Notify API URL and replaces with Notify.gov
* Improves the error handler for HTTPErrors to provide actual exception and stack trace information

Signed-off-by: Carlo Costino <carlo.costino@gsa.gov>

app/config.py

@@ -19,9 +19,7 @@ class Config(object):
     HEADER_COLOUR = (
         "#81878b"  # mix of dark-grey and mid-grey
     )
-    LOGO_CDN_DOMAIN = (
-        "static-logos.notifications.service.gov.uk"  # TODO use our own CDN
-    )
+
     ASSETS_DEBUG = False
 
     # Credentials