Refactored register_errorhandlers so that it handles HTTPError

Remove most cases where we catch HTTPError

app/main/views/verify.py

@@ -2,12 +2,9 @@ from flask import (
     render_template,
     redirect,
     session,
-    url_for,
-    abort
+    url_for
 )
 
-from notifications_python_client.errors import HTTPError
-
 from flask_login import login_user
 
 from app.main import main
@@ -31,11 +28,6 @@ def verify():
             activated_user = users_dao.activate_user(user)
             login_user(activated_user)
             return redirect(url_for('main.add_service', first='first'))
-        except HTTPError as e:
-            if e.status_code == 404:
-                abort(404)
-            else:
-                raise e
         finally:
             del session['user_details']