fix(system_python): Remove printing of not always present attribute (bazel-contrib#3781)

This attribute is not part of the Python public API and in Debian 10
Buster (OpenJDK 11, gcc 8.3.0) it seems to not be defined.

This reverts one of the debug logging statements added in
bazel-contrib#3667

Fixes bazel-contrib#3774

---------

Co-authored-by: Ignas Anikevicius <240938+aignas@users.noreply.github.com>

Author: limdor

CHANGELOG.md

@@ -84,6 +84,9 @@ END_UNRELEASED_TEMPLATE
 * (pypi) Fix `importlib.metadata.files` by ensuring `RECORD` is included in
   installed wheel targets, except when built from sdist
   ([#3024](https://github.com/bazel-contrib/rules_python/issues/3024)).
+* (system_python) Fix AttributeError exception on Debian 10 Buster
+  python installations which may not set `sys._base_executable`
+  ([#3774](https://github.com/bazel-contrib/rules_python/issues/3774)).
 * (windows) Fix `py_test`/`py_binary` failure when the target name contains
   path separators; the bootstrap stub is now declared as a sibling of the
   `.exe` launcher
@@ -92,7 +95,6 @@ END_UNRELEASED_TEMPLATE
   towards the underlying `*.update` target.
   ([#3787](https://github.com/bazel-contrib/rules_python/pull/3787))
 
-
 {#v0-0-0-added}
 ### Added
 * (toolchain) Added {obj}`python.override.toolchain_target_settings` to allow

python/private/python_bootstrap_template.txt

@@ -568,7 +568,7 @@ def main():
   print_verbose("VENV_REL_SITE_PACKAGES:", VENV_REL_SITE_PACKAGES)
   print_verbose("WORKSPACE_NAME:", WORKSPACE_NAME )
   print_verbose("bootstrap sys.executable:", sys.executable)
-  print_verbose("bootstrap sys._base_executable:", sys._base_executable)
+  print_verbose("bootstrap sys._base_executable:", getattr(sys, "_base_executable", "unknown"))
   print_verbose("bootstrap sys.version:", sys.version)
 
   args = sys.argv[1:]