Leave the global responses configuration alone (#3529)

Instead of modifying responses._default_mock, create our own
responses.RequestsMock object that we can modify as needed without
interfering with other users of the responses library.

Fixes #3264.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

tests/test_apigateway/test_apigateway.py

@@ -8,9 +8,9 @@ import requests
 import sure  # noqa
 from botocore.exceptions import ClientError
 
-import responses
 from moto import mock_apigateway, mock_cognitoidp, settings
 from moto.core import ACCOUNT_ID
+from moto.core.models import responses_mock
 import pytest
 
 
@@ -1786,8 +1786,8 @@ def test_get_model_with_invalid_name():
 
 @mock_apigateway
 def test_http_proxying_integration():
-    responses.add(
-        responses.GET, "http://httpbin.org/robots.txt", body="a fake response"
+    responses_mock.add(
+        responses_mock.GET, "http://httpbin.org/robots.txt", body="a fake response"
     )
 
     region_name = "us-west-2"

tests/test_sns/test_publishing_boto3.py

@@ -8,11 +8,11 @@ import re
 from freezegun import freeze_time
 import sure  # noqa
 
-import responses
 from botocore.exceptions import ClientError
 import pytest
 from moto import mock_sns, mock_sqs, settings
 from moto.core import ACCOUNT_ID
+from moto.core.models import responses_mock
 from moto.sns import sns_backend
 
 MESSAGE_FROM_SQS_TEMPLATE = (
@@ -332,7 +332,7 @@ def test_publish_to_http():
         json.loads.when.called_with(request.body.decode()).should_not.throw(Exception)
         return 200, {}, ""
 
-    responses.add_callback(
+    responses_mock.add_callback(
         method="POST", url="http://example.com/foobar", callback=callback
     )