Debug setup.py issue

Author: mkruskal-google

python/dist/BUILD.bazel

@@ -284,6 +284,7 @@ genrule(
     outs = ["protobuf-%s.tar.gz" % PROTOBUF_PYTHON_VERSION],
     cmd = """
         export PYTHONPATH=$$PWD/external/pip_deps_setuptools/site-packages
+        echo $PYTHONPATH
         set -eux
         tar -xzvf $(location :source_tarball)
         cd protobuf/