docs: def get_environment_vars(filename):
      """Return a dict of environment variables required to run a service under faketime."""
      if sys.platform == "linux" or sys.platform == "linux2":
          return {
              'LD_PRELOAD': path.join(LIBFAKETIME_DIR, "libfaketime.so.1"),
              'FAKETIME_SKIP_CMDS': 'nodejs',     # node doesn't seem to work in the current version.
              'FAKETIME_TIMESTAMP_FILE': filename,
          }
      elif sys.platform == "darwin":
          return {
              'DYLD_INSERT_LIBRARIES': path.join(LIBFAKETIME_DIR, "libfaketime.1.dylib"),
              'DYLD_FORCE_FLAT_NAMESPACE': '1',
              'FAKETIME_TIMESTAMP_FILE': filename,
          }
      else:
          raise RuntimeError("libfaketime does not support '{}' platform".format(sys.platform))