fix: make requests import conditional for gce universe domain (#1476)

* fix: make requests import conditional for gce universe domain

* remove if for creating request object

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

---------

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

google/auth/compute_engine/credentials.py

@@ -28,7 +28,6 @@
 from google.auth import jwt
 from google.auth import metrics
 from google.auth.compute_engine import _metadata
-from google.auth.transport import requests as google_auth_requests
 from google.oauth2 import _client
 
 
@@ -84,7 +83,6 @@ def __init__(
         self._scopes = scopes
         self._default_scopes = default_scopes
         self._universe_domain_cached = False
-        self._universe_domain_request = google_auth_requests.Request()
         if universe_domain:
             self._universe_domain = universe_domain
             self._universe_domain_cached = True
@@ -150,8 +148,11 @@ def requires_scopes(self):
     def universe_domain(self):
         if self._universe_domain_cached:
             return self._universe_domain
+
+        from google.auth.transport import requests as google_auth_requests
+
         self._universe_domain = _metadata.get_universe_domain(
-            self._universe_domain_request
+            google_auth_requests.Request()
         )
         self._universe_domain_cached = True
         return self._universe_domain

tests/compute_engine/test_credentials.py

@@ -257,16 +257,12 @@ def test_universe_domain(self, get_universe_domain):
         assert self.credentials.universe_domain == "fake_universe_domain"
         assert self.credentials._universe_domain == "fake_universe_domain"
         assert self.credentials._universe_domain_cached
-        get_universe_domain.assert_called_once_with(
-            self.credentials._universe_domain_request
-        )
+        get_universe_domain.assert_called_once()
 
         # calling the universe_domain property the second time should use the
         # cached value instead of calling get_universe_domain
         assert self.credentials.universe_domain == "fake_universe_domain"
-        get_universe_domain.assert_called_once_with(
-            self.credentials._universe_domain_request
-        )
+        get_universe_domain.assert_called_once()
 
     @mock.patch("google.auth.compute_engine._metadata.get_universe_domain")
     def test_user_provided_universe_domain(self, get_universe_domain):