chore(generator): add local google-api-core path override to noxfile showcase tests

Injects local workspace path override for google-api-core package to allow running showcase unit tests successfully when new changes are introduced to api-core.

Author: hebaalazzeh

packages/gapic-generator/noxfile.py

@@ -30,6 +30,8 @@
 from os import path
 import shutil
 
+CURRENT_DIRECTORY = Path(__file__).parent.absolute()
+
 
 nox.options.error_on_missing_interpreters = True
 
@@ -487,6 +489,14 @@ def run_showcase_unit_tests(session, fail_under=100, rest_async_io_enabled=False
     # Freeze and print python environment package versions
     session.run("python", "-m", "pip", "freeze")
 
+    google_api_core_dir = next(
+        (str(p / "packages" / "google-api-core") for p in CURRENT_DIRECTORY.parents if (p / "packages" / "google-api-core").exists()),
+        None
+    )
+    if google_api_core_dir:
+        session.run("pip", "uninstall", "google-api-core", "-y")
+        session.install("-e", google_api_core_dir, "--no-deps")
+
     # Run the tests.
     session.run(
         "py.test",