test(gcp): Only run GCP tests when they should (#3721)

GCP tests have been running in our common test suite, including on Python versions other than 3.7 (the only version which supports the GCP integration), even though we have a separate `py3.7-gcp` tox environment for these tests. The tests take a long time, so only executing in the appropriate `tox` environment should speed up CI time.

Co-authored-by: Anton Pirker <[email protected]>

Author: szokeasaurusrex

tests/integrations/gcp/__init__.py

@@ -0,0 +1,6 @@
+import pytest
+import os
+
+
+if "gcp" not in os.environ.get("TOX_ENV_NAME", ""):
+    pytest.skip("GCP tests only run in GCP environment", allow_module_level=True)