Reraise integrity errors on org name unique contraints as 400

- currently being raised as 500s, but should really be 400s as the request data has the duplicate name

app/organisation/rest.py

@@ -1,4 +1,5 @@
-from flask import Blueprint, jsonify, request
+from flask import Blueprint, current_app, jsonify, request
+from sqlalchemy.exc import IntegrityError
 
 from app.dao.organisation_dao import (
     dao_create_organisation,
@@ -22,6 +23,21 @@ organisation_blueprint = Blueprint('organisation', __name__)
 register_errors(organisation_blueprint)
 
 
+@organisation_blueprint.errorhandler(IntegrityError)
+def handle_integrity_error(exc):
+    """
+    Handle integrity errors caused by the unique contraint on ix_organisation_name
+    """
+    if 'ix_organisation_name' in str(exc):
+        current_app.logger.exception('Unique constraint ix_organisation_name triggered')
+        return jsonify(
+            result='error',
+            message='Organisation name already exists'
+        ), 400
+
+    raise
+
+
 @organisation_blueprint.route('', methods=['GET'])
 def get_organisations():
     organisations = [

tests/app/organisation/test_rest.py

@@ -53,6 +53,24 @@ def test_post_create_organisation(admin_request, notify_db_session):
     assert len(organisation) == 1
 
 
+def test_post_create_organisation_existing_name_raises_400(admin_request, sample_organisation):
+    data = {
+        'name': sample_organisation.name,
+        'active': True
+    }
+
+    response = admin_request.post(
+        'organisation.create_organisation',
+        _data=data,
+        _expected_status=400
+    )
+
+    organisation = Organisation.query.all()
+
+    assert len(organisation) == 1
+    assert response['message'] == 'Organisation name already exists'
+
+
 def test_post_create_organisation_with_missing_name_gives_validation_error(admin_request, notify_db_session):
     data = {
         'active': False
@@ -91,6 +109,24 @@ def test_post_update_organisation_updates_fields(admin_request, notify_db_sessio
     assert organisation[0].active == data['active']
 
 
+def test_post_update_organisation_raises_400_on_existing_org_name(
+        admin_request, notify_db_session, sample_organisation):
+    org = create_organisation()
+    data = {
+        'name': sample_organisation.name,
+        'active': False
+    }
+
+    response = admin_request.post(
+        'organisation.update_organisation',
+        _data=data,
+        organisation_id=org.id,
+        _expected_status=400
+    )
+
+    assert response['message'] == 'Organisation name already exists'
+
+
 def test_post_update_organisation_gives_404_status_if_org_does_not_exist(admin_request, notify_db_session):
     data = {'name': 'new organisation name'}