doc: Update code style guide for Python 3 and docstrings (RobotLocomo…

…tion#12236)

workspace: Bump styleguide fork to latest

doc/code_style_guide.rst

@@ -44,9 +44,17 @@ incorporates `PEP 257 -- Docstring Conventions
 <https://www.python.org/dev/peps/pep-0257/>`_, Drake follows its
 recommendations as well.
 
+Drake also follows the
+`RobotLocomotion fork <https://drake.mit.edu/styleguide/pyguide.html>`_
+of the Google Python Style Guide. Please refer to that page for the sections
+that are adhered to, and the relevant exceptions.
+
 See :ref:`tools for complying with coding style <code-style-tools>` for details
 about the automated style checks.
 
+.. TODO(eric.cousineau): Move these clarifications and exceptions to styleguide
+   repo.
+
 .. _code-style-guide-python-clarifications:
 
 Clarifications
@@ -88,7 +96,7 @@ Additional Rules
 
   Rationale: ``/usr/bin/env`` enables a ``PATH`` search for the Python 3
   executable. This is also recommended by
-  `PEP 394 <https://www.python.org/dev/peps/pep-0394/>`_`.
+  `PEP 394 <https://www.python.org/dev/peps/pep-0394/>`_.
 
 .. [#bazel_py_script] Generally, this means scripts that run via ``bazel run``,
    ``bazel test``, or ``./bazel-bin/...``.

tools/workspace/styleguide/repository.bzl

@@ -8,8 +8,8 @@ def styleguide_repository(
     github_archive(
         name = name,
         repository = "RobotLocomotion/styleguide",
-        commit = "97ac1c4e58c06f9c774ed02321cf716a21e0342d",
-        sha256 = "7d8adeac7b659ec082f8e1147301be431980f4c3116d3e6b1def691fccbbf47e",  # noqa
+        commit = "47a6f403e7a6ed5e44e7875bcec4d27815063029",
+        sha256 = "68344607a14230ede11b4dcf886ed9bef6df2c339f32ec724591a94e5d5f2e6b",  # noqa
         build_file = "@drake//tools/workspace/styleguide:package.BUILD.bazel",
         mirrors = mirrors,
     )