Add a new environment variable GRPC_BAZEL_BUILD

src/python/grpcio_tests/tests/bazel_namespace_package_hack.py

@@ -24,8 +24,8 @@ import sys
 # Analysis in depth: https://github.com/bazelbuild/rules_python/issues/55
 def sys_path_to_site_dir_hack():
     """Add valid sys.path item to site directory to parse the .pth files."""
-    # If not running under Bazel, return.
-    if 'RUN_UNDER_RUNFILES' not in os.environ:
+    # GRPC_BAZEL_BUILD is explicitly set by tools/bazel.rc.
+    if 'GRPC_BAZEL_BUILD' not in os.environ:
         return
     for item in sys.path:
         if os.path.exists(item):

tools/bazel.rc

@@ -5,6 +5,7 @@
 
 build --client_env=CC=clang
 build --copt=-DGRPC_BAZEL_BUILD
+build --action_env=GRPC_BAZEL_BUILD=1
 
 build:opt --compilation_mode=opt
 build:opt --copt=-Wframe-larger-than=16384