Add exception handler for when pfctl operations fail

tests/test_flush.py

@@ -1,5 +1,6 @@
 import base64
 from types import SimpleNamespace
+from subprocess import CalledProcessError
 
 
 def test_flush(client, mocker):
@@ -19,3 +20,19 @@ def test_flush(client, mocker):
                           headers={"Authorization": "Basic " + valid_credentials})
 
     assert response.json['operation'] == 'flush'
+
+
+def test_flush_nonexistent(client, mocker):
+
+    cmd = ['/usr/local/bin/sudo', '/sbin/pfctl', '-a', 'some/anchor', '-t', 'nonexistent', '-T', 'flush']
+
+    mocker.patch('jail2ban.pfctl.run',
+                 side_effect=CalledProcessError(255, cmd, output=b'',
+                                                stderr=b'pfctl: Table does not exist'))
+
+    valid_credentials = base64.b64encode(b"test.example.com:testpassword").decode("utf-8")
+    name = 'nonexistent'
+    response = client.get(f"/flush/{name}",
+                          headers={"Authorization": "Basic " + valid_credentials})
+
+    assert 'error' in response.json