message: Make modifications of WORKSPACE by setup.py more explicit.
  This allows setup.py to overwrite the tink_base and tink_cc WORKSPACE paths in a more robust way and adds a note that it has been modified.
diff: @@ -15,14 +15,15 @@ from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  +from distutils import spawn
  import glob
  import os
  import posixpath
  +import re
  import shutil
  import subprocess
  import sys
  -from distutils import spawn
  import setuptools
  from setuptools.command import build_ext
  @@ -117,6 +118,17 @@ def _patch_workspace(workspace_content):
  # This replaces the paths with the latest http_archive.
  # In order to override this with a local WORKSPACE use the TINK_BASE_PATH
  # environment variable.
  +
  + if 'TINK_PYTHON_SETUPTOOLS_OVERRIDE_BASE_PATH' in os.environ:
  + base_path = os.environ['TINK_PYTHON_SETUPTOOLS_OVERRIDE_BASE_PATH']
  + workspace_content = re.sub(r'(?<="tink_base",\n path = ").*(?=\n)',
  + base_path + '", # Modified by setup.py',
  + workspace_content)
  + workspace_content = re.sub(r'(?<="tink_cc",\n path = ").*(?=\n)',
  + base_path + '/cc' + '", # Modified by setup.py',
  + workspace_content)
  + else:
  + # If not base is specified use the latest version from GitHub
  base = ('local_repository(\n'
  ' name = "tink_base",\n'
  ' path = "..",\n'
  @@ -127,20 +139,8 @@ def _patch_workspace(workspace_content):
  ' path = "../cc",\n'
  ')\n')
  - if 'TINK_PYTHON_SETUPTOOLS_OVERRIDE_BASE_PATH' in os.environ:
  - base_path = os.environ['TINK_PYTHON_SETUPTOOLS_OVERRIDE_BASE_PATH']
  - base_patched = ('local_repository(\n'
  - ' name = "tink_base",\n'
  - ' path = "{}",\n'
  - ')\n'.format(base_path))
  -
  - cc_patched = ('local_repository(\n'
  - ' name = "tink_cc",\n'
  - ' path = "{}/cc",\n'
  - ')\n'.format(base_path))
  - else:
  - # If not base is specified use the latest version from GitHub
  base_patched = (
  + '# Modified by setup.py\n'
  'http_archive(\n'
  ' name = "tink_base",\n'
  ' urls = ["https://github.com/google/tink/archive/master.zip"],\n'
  @@ -148,6 +148,7 @@ def _patch_workspace(workspace_content):
  ')\n')
  cc_patched = (
  + '# Modified by setup.py\n'
  'http_archive(\n'
  ' name = "tink_cc",\n'
  ' urls = ["https://github.com/google/tink/archive/master.zip"],\n'
  