policies/expression: fix ip_network not being imported by default

docs/policies/expression.md

@@ -26,7 +26,11 @@ return False
     - `request.obj`: A Django Model instance. This is only set if the policy is ran against an object.
     - `request.context`: A dictionary with dynamic data. This depends on the origin of the execution.
 - `pb_is_sso_flow`: Boolean which is true if request was initiated by authenticating through an external provider.
-- `pb_client_ip`: Client's IP Address or '255.255.255.255' if no IP Address could be extracted. Can be [compared](../expressions/index.md#comparing-ip-addresses)
+- `pb_client_ip`: Client's IP Address or 255.255.255.255 if no IP Address could be extracted. Can be [compared](../expressions/index.md#comparing-ip-addresses), for example
+
+    ```python
+    return pb_client_ip in ip_network('10.0.0.0/24')
+    ```
 
 Additionally, when the policy is executed from a flow, every variable from the flow's current context is accessible under the `context` object.
 

passbook/policies/expression/evaluator.py

@@ -1,5 +1,5 @@
 """passbook expression policy evaluator"""
-from ipaddress import ip_address
+from ipaddress import ip_address, ip_network
 from typing import List
 
 from django.http import HttpRequest
@@ -22,6 +22,8 @@ class PolicyEvaluator(BaseEvaluator):
         super().__init__()
         self._messages = []
         self._context["pb_message"] = self.expr_func_message
+        self._context["ip_address"] = ip_address
+        self._context["ip_network"] = ip_network
         self._filename = policy_name or "PolicyEvaluator"
 
     def expr_func_message(self, message: str):