Use pytest_configure to set mock responses as global variable (#429)

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**What this PR does / why we need it**:
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In #404, we merge mock_oauth in client_test.py and merlin_test.py to one
pytest fixture in conftest.py. However, there's an issue where the mock
responses in conftest is not used by client_test or merlin_test because
it was using different instance of Reponses object.

This PR introduce
[pytest_configure()](https://docs.pytest.org/en/7.1.x/reference/reference.html#pytest.hookspec.pytest_configure)
function where it sets mock responses as global variable that can be
called by other files.

**Does this PR introduce a user-facing change?**:
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```release-note
NONE
```

**Checklist**

- [x] Updated unit test, integration, and/or e2e tests
- [x] Tested locally
- [ ] Updated documentation
- [ ] Update Swagger spec if the PR introduce API changes
- [ ] Regenerated Golang and Python client if the PR introduce API
changes

python/sdk/test/client_test.py

@@ -18,7 +18,6 @@
 from unittest import mock
 
 import pytest
-from urllib3_mock import Responses
 
 import client as cl
 from client import ApiClient, Configuration
@@ -28,7 +27,8 @@
 from merlin.util import guess_mlp_ui_url
 from merlin.version import VERSION
 
-responses = Responses("requests.packages.urllib3")
+# get global mock responses that configured in conftest
+responses = pytest.responses
 
 
 @pytest.fixture

python/sdk/test/conftest.py

@@ -14,18 +14,27 @@
 
 import os
 
+import mlflow
 import pytest
 import requests as requests_lib
 from requests.adapters import HTTPAdapter
 from requests.packages.urllib3.util.retry import Retry
 from urllib3_mock import Responses
 
 import client as cl
-import mlflow
 from client import ApiClient, Configuration
 from merlin.model import Model, ModelType, ModelVersion, Project
 
 
+# From the documentation (https://docs.pytest.org/en/7.1.x/reference/reference.html#pytest.hookspec.pytest_configure):
+# Allow plugins and conftest files to perform initial configuration.
+# This hook is called for every plugin and initial conftest file after command line options have been parsed.
+# After that, the hook is called for other conftest files as they are imported.
+def pytest_configure():
+ # share mock responses as global variable so it can be reused and called as decorator on other files.
+ pytest.responses = Responses("requests.packages.urllib3")
+
+
 @pytest.fixture
 def url():
  return "http://127.0.0.1:8080"
@@ -137,11 +146,10 @@ def requests():
  return req
 
 
-responses = Responses("requests.packages.urllib3")
-
-
 @pytest.fixture
 def mock_oauth():
+ responses = pytest.responses
+
  responses.add(
  "GET",
  "/computeMetadata/v1/instance/service-accounts/default/",

python/sdk/test/merlin_test.py

@@ -14,15 +14,15 @@
 
 import json
 
+import mlflow
 import pytest
-from urllib3_mock import Responses
 
 import client as cl
 import merlin
-import mlflow
 from merlin.model import ModelVersion
 
-responses = Responses("requests.packages.urllib3")
+# get global mock responses that configured in conftest
+responses = pytest.responses
 
 default_resource_request = cl.ResourceRequest(1, 1, "100m", "128Mi")
 env_1 = cl.Environment(