WIP: Try pinning api-core to 2.11.0 for tests

Author: vchudnov-g

noxfile.py

@@ -125,7 +125,6 @@ def __call__(self, frag):
                     str(frag),
                     external=True,
                     silent=True,
-                    env={"PYTHONWARNINGS": "ignore"},
                 )
             )
 
@@ -174,7 +173,9 @@ def fragment(session, use_ads_templates=False):
     )
     session.install("-e", ".")
 
-
+    # The specific failure is `Plugin output is unparseable`
+    if session.python in ("3.9", "3.10"):
+        session.install("google-api-core-2.11.0")
 
     frag_files = (
         [Path(f) for f in session.posargs] if session.posargs else FRAGMENT_FILES
@@ -242,7 +243,9 @@ def showcase_library(
     # TODO(https://github.com/googleapis/gapic-generator-python/issues/2473):
     # Warnings emitted from google-api-core starting in 2.28
     # appear to cause issues when running protoc.
-
+    # The specific failure is `Plugin output is unparseable`
+    if session.python in ("3.9", "3.10"):
+        session.install("google-api-core=2.11.0")
 
     # Install a client library for Showcase.
     with tempfile.TemporaryDirectory() as tmp_dir:
@@ -335,7 +338,6 @@ def showcase_library(
         session.run(
             *cmd_tup,
             external=True,
-            env={"PYTHONWARNINGS": "ignore"},
         )
 
         # Install the generated showcase library.