Do not make use of pytest.warns(None)

pytest.warns(None) is an anti-pattern, and there are easier ways to
accomplish both cases with how the code is leveraging pytest.warns().
Firstly, it can match on a specific warning and will assert that the
warning is raised -- and it doesn't need to be used if we want to assert
code raises no warnings, the standard library can do that directly.
Furthermore, pytest.warns(None) is an error in Pytest 8 and above.

jenkinsapi_tests/unittests/test_build.py

@@ -1,3 +1,4 @@
+import warnings
 import requests
 import pytest
 import pytz
@@ -258,14 +259,12 @@ def fake_get_data(cls, tree=None, params=None):
     monkeypatch.setattr(Build, "get_data", fake_get_data)
 
     with pytest.raises(requests.HTTPError) as excinfo:
-        with pytest.warns(None) as record:
+        with pytest.warns(
+            UserWarning,
+            match="Make sure the Environment Injector plugin is installed."
+        ):
             build.get_env_vars()
     assert "404" == str(excinfo.value)
-    assert len(record) == 1
-    expected = UserWarning(
-        "Make sure the Environment Injector " "plugin is installed."
-    )
-    assert str(record[0].message) == str(expected)
 
 
 def test_build_env_vars_other_exception(monkeypatch, build):
@@ -275,10 +274,10 @@ def fake_get_data(cls, tree=None, params=None):
     monkeypatch.setattr(Build, "get_data", fake_get_data)
 
     with pytest.raises(Exception) as excinfo:
-        with pytest.warns(None) as record:
+        with warnings.catch_warnings():
+            warnings.simplefilter("error")
             build.get_env_vars()
     assert "" == str(excinfo.value)
-    assert len(record) == 0
 
 
 def test_build_get_status(build) -> None: