Make log spam test run and pass in Cloud TPU CI

.github/workflows/cloud-tpu-ci-nightly.yml

@@ -88,6 +88,9 @@ jobs:
             --maxfail=20 -m "not multiaccelerator" tests examples
           # Run multi-accelerator across all chips
           python3 -m pytest --tb=short --maxfail=20 -m "multiaccelerator" tests
+          # This test needs to be run by itself because it starts a subprocess
+          # that needs to access the TPU (only one process can use the TPU at a time)
+          python3 test/logging_test.py LoggingTest.test_no_log_spam
       - name: Send chat on failure
         # Don't notify when testing the workflow from a branch.
         if: ${{ (failure() || cancelled()) && github.ref_name == 'main' && matrix.jaxlib-version != 'nightly+oldest_supported_libtpu' }}

jax/_src/cloud_tpu_init.py

@@ -66,14 +66,3 @@ def cloud_tpu_init() -> None:
   os.environ.setdefault('GRPC_VERBOSITY', 'ERROR')
   os.environ.setdefault('JAX_PLATFORMS', 'tpu,cpu')
   os.environ['TPU_ML_PLATFORM'] = 'JAX'
-
-  # TODO(skyewm): remove this warning at some point, say around Sept 2023.
-  use_pjrt_c_api = os.environ.get('JAX_USE_PJRT_C_API_ON_TPU', None)
-  if use_pjrt_c_api:
-    warnings.warn(
-        "JAX_USE_PJRT_C_API_ON_TPU no longer has an effect (the new TPU "
-        "runtime is always enabled now). Unset the environment variable "
-        "to disable this warning.")
-
-  # Remove when minimum jaxlib version is >= 0.4.15
-  os.environ['JAX_USE_PJRT_C_API_ON_TPU'] = "true"

tests/logging_test.py

@@ -15,6 +15,7 @@
 import contextlib
 import io
 import logging
+import os
 import subprocess
 import sys
 import textwrap
@@ -69,8 +70,10 @@ def test_no_log_spam(self):
     python = sys.executable
     assert "python" in python
     # Make sure C++ logging is at default level for the test process.
+    new_env = dict(os.environ)
+    new_env["TF_CPP_MIN_LOG_LEVEL"] = "1"
     proc = subprocess.run([python, "-c", program], capture_output=True,
-                          env={"TF_CPP_MIN_LOG_LEVEL": "1"})
+                          env=new_env)
 
     lines = proc.stdout.split(b"\n")
     lines.extend(proc.stderr.split(b"\n"))