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>

moto/apigateway/models.py

@@ -41,6 +41,7 @@ from .exceptions import (
     RestAPINotFound,
     ModelNotFound,
 )
+from ..core.models import responses_mock
 
 STAGE_URL = "https://{api_id}.execute-api.{region_name}.amazonaws.com/{stage_name}"
 
@@ -565,7 +566,7 @@ class RestAPI(BaseModel):
         )
 
         for url in [stage_url_lower, stage_url_upper]:
-            responses._default_mock._matches.insert(
+            responses_mock._matches.insert(
                 0,
                 responses.CallbackResponse(
                     url=url,

moto/core/models.py

@@ -248,7 +248,7 @@ botocore_mock = responses.RequestsMock(
     target="botocore.vendored.requests.adapters.HTTPAdapter.send",
 )
 
-responses_mock = responses._default_mock
+responses_mock = responses.RequestsMock(assert_all_requests_are_fired=False)
 # Add passthrough to allow any other requests to work
 # Since this uses .startswith, it applies to http and https requests.
 responses_mock.add_passthru("http")