diff --git a/passbook/core/templates/partials/form.html b/passbook/core/templates/partials/form.html
index 83a6e8ae3..efd249d08 100644
--- a/passbook/core/templates/partials/form.html
+++ b/passbook/core/templates/partials/form.html
@@ -2,6 +2,13 @@
 {% load i18n %}
 
 {% csrf_token %}
+{% if form.non_field_errors %}
+<div class="pf-c-form__group has-error">
+    <p class="pf-c-form__helper-text pf-m-error">
+        {{ form.non_field_errors }}
+    </p>
+</div>
+{% endif %}
 {% for field in form %}
 <div class="pf-c-form__group {% if field.errors %} has-error {% endif %}">
     {% if field.field.widget|fieldtype == 'RadioSelect' %}
diff --git a/passbook/policies/expression/evaluator.py b/passbook/policies/expression/evaluator.py
index 047c5f1ac..2a0fa8904 100644
--- a/passbook/policies/expression/evaluator.py
+++ b/passbook/policies/expression/evaluator.py
@@ -1,6 +1,6 @@
 """passbook expression policy evaluator"""
 import re
-from typing import TYPE_CHECKING, Any, Dict, List, Optional
+from typing import Any, Dict, List, Optional
 
 from django.core.exceptions import ValidationError
 from django.http import HttpRequest
@@ -10,14 +10,12 @@ from jinja2.nativetypes import NativeEnvironment
 from requests import Session
 from structlog import get_logger
 
+from passbook.core.models import User
 from passbook.flows.planner import PLAN_CONTEXT_SSO
 from passbook.flows.views import SESSION_KEY_PLAN
 from passbook.lib.utils.http import get_client_ip
 from passbook.policies.types import PolicyRequest, PolicyResult
 
-if TYPE_CHECKING:
-    from passbook.core.models import User
-
 LOGGER = get_logger()
 
 
@@ -43,6 +41,7 @@ class Evaluator:
         self._env.globals["pb_message"] = self.jinja2_func_message
         self._context = {
             "pb_is_group_member": Evaluator.jinja2_func_is_group_member,
+            "pb_user_by": Evaluator.jinja2_func_user_by,
             "pb_logger": get_logger(),
             "requests": Session(),
         }
@@ -64,7 +63,15 @@ class Evaluator:
         return re.sub(regex, repl, value)
 
     @staticmethod
-    def jinja2_func_is_group_member(user: "User", group_name: str) -> bool:
+    def jinja2_func_user_by(**filters) -> Optional[User]:
+        """Get user by filters"""
+        users = User.objects.filter(**filters)
+        if users:
+            return users.first()
+        return None
+
+    @staticmethod
+    def jinja2_func_is_group_member(user: User, group_name: str) -> bool:
         """Check if `user` is member of group with name `group_name`"""
         return user.groups.filter(name=group_name).exists()
 
@@ -126,4 +133,4 @@ class Evaluator:
             self._env.from_string(expression)
             return True
         except TemplateSyntaxError as exc:
-            raise ValidationError("Expression Syntax Error") from exc
+            raise ValidationError(f"Expression Syntax Error: {str(exc)}") from exc
diff --git a/passbook/policies/types.py b/passbook/policies/types.py
index 1fd65e63b..29bf02932 100644
--- a/passbook/policies/types.py
+++ b/passbook/policies/types.py
@@ -39,4 +39,6 @@ class PolicyResult:
         self.messages = messages
 
     def __str__(self):
-        return f"<PolicyResult passing={self.passing}>"
+        if self.messages:
+            return f"PolicyResult passing={self.passing} messages={self.messages}"
+        return f"PolicyResult passing={self.passing}"
diff --git a/passbook/stages/prompt/forms.py b/passbook/stages/prompt/forms.py
index 7347e9053..e9157d198 100644
--- a/passbook/stages/prompt/forms.py
+++ b/passbook/stages/prompt/forms.py
@@ -64,4 +64,4 @@ class PromptForm(forms.Form):
         engine.build()
         result = engine.result
         if not result.passing:
-            raise forms.ValidationError(result.messages)
+            raise forms.ValidationError(list(result.messages))