[CHORE] flake8 issues E402, E721 and F821 (#1874)

* F821: undefine name
disabled and logged webhook_listener for opennode and lnpay because they are obviously not working
* E402: module level import not at top of file
* E721 fixes, only popped up for python3.9 not 3.10

tests/core/views/test_api.py

@@ -285,7 +285,7 @@ async def test_decode_invoice(client, invoice):
 async def test_api_payment_without_key(invoice):
     # check the payment status
     response = await api_payment(invoice["payment_hash"])
-    assert type(response) == dict
+    assert isinstance(response, dict)
     assert response["paid"] is True
     # no key, that's why no "details"
     assert "details" not in response
@@ -298,7 +298,7 @@ async def test_api_payment_with_key(invoice, inkey_headers_from):
     response = await api_payment(
         invoice["payment_hash"], inkey_headers_from["X-Api-Key"]
     )
-    assert type(response) == dict
+    assert isinstance(response, dict)
     assert response["paid"] is True
     assert "details" in response