also patch showcase_w_rest_async

Author: parthea

noxfile.py

@@ -424,7 +424,9 @@ def showcase_w_rest_async(
     with showcase_library(
         session, templates=templates, other_opts=other_opts, rest_async_io_enabled=True
     ):
-        session.install("pytest", "pytest-asyncio")
+        # Exclude pytest-asyncio==1.0.0 while we investigate the recent failure described in
+        # https://github.com/googleapis/gapic-generator-python/issues/2399
+        session.install("pytest", "pytest-asyncio!=1.0.0")
         test_directory = Path("tests", "system")
         ignore_file = env.get("IGNORE_FILE")
         pytest_command = [