Users can be invited with no permissions

app/main/views/manage_users.py

@@ -77,6 +77,11 @@ def invite_user(service_id, user_id=None):
         form.login_authentication.data = "sms_auth"
 
     if form.validate_on_submit():
+        if not form.permissions or len(form.permissions) == 0:
+            return render_template(
+                "views/user-has-no-permissions.html",
+                user_to_invite=user_to_invite,
+            )
         email_address = form.email_address.data
         invited_user = InvitedUser.create(
             current_user.id,

app/templates/views/user-has-no-permissions.html

@@ -0,0 +1,22 @@
+{% extends "withnav_template.html" %}
+{% from "components/page-header.html" import page_header %}
+{% from "components/components/back-link/macro.njk" import usaBackLink %}
+
+{% block service_page_title %}
+  You must specify at least one permission for the user.
+{% endblock %}
+
+{% block backLink %}
+  {{ usaBackLink({ "href": url_for('main.manage_users', service_id=current_service.id) }) }}
+{% endblock %}
+
+{% block maincolumn_content %}
+
+  {{ page_header('This person has no permissions') }}
+
+  <p class="usa-body">
+    Your invited user currently has no permissions for
+    ‘{{ current_service.name }}’. Please specify grant some permissions to the user.
+  </p>
+
+{% endblock %}