Add support for IoT detach_policy

moto/iot/models.py

@@ -445,6 +445,15 @@ class IoTBackend(BaseBackend):
             return
         self.principal_policies[k] = (principal, policy)
 
+    def detach_policy(self, policy_name, target):
+        # this may raises ResourceNotFoundException
+        self._get_principal(target)
+        self.get_policy(policy_name)
+        k = (target, policy_name)
+        if k not in self.principal_policies:
+            raise ResourceNotFoundException()
+        del self.principal_policies[k]
+
     def detach_principal_policy(self, policy_name, principal_arn):
         # this may raises ResourceNotFoundException
         self._get_principal(principal_arn)

moto/iot/responses.py

@@ -242,6 +242,15 @@ class IoTResponse(BaseResponse):
         )
         return json.dumps(dict())
 
+    def detach_policy(self):
+        policy_name = self._get_param("policyName")
+        target = self._get_param('target')
+        self.iot_backend.detach_policy(
+            policy_name=policy_name,
+            target=target,
+        )
+        return json.dumps(dict())
+
     def detach_principal_policy(self):
         policy_name = self._get_param("policyName")
         principal = self.headers.get('x-amzn-iot-principal')