Send HTTP header as well as inserting meta tag

This will let us use the decorator on endpoints that don’t return HTML.

app/utils.py

@@ -16,7 +16,16 @@ import pyexcel
 import pyexcel_xlsx
 import pytz
 from dateutil import parser
-from flask import abort, current_app, g, redirect, request, session, url_for
+from flask import (
+    abort,
+    current_app,
+    g,
+    make_response,
+    redirect,
+    request,
+    session,
+    url_for,
+)
 from flask_login import current_user, login_required
 from notifications_utils.field import Field
 from notifications_utils.formatters import (
@@ -773,5 +782,7 @@ def hide_from_search_engines(f):
     @wraps(f)
     def decorated_function(*args, **kwargs):
         g.hide_from_search_engines = True
-        return f(*args, **kwargs)
+        response = make_response(f(*args, **kwargs))
+        response.headers['X-Robots-Tag'] = 'noindex'
+        return response
     return decorated_function