code: def svn_versions_from_vcs(tag_prefix, root, verbose=False):
      
  
      if not os.path.exists(os.path.join(root, '.svn')):
          if verbose:
              print("no .svn in %s." % root)
          return {}
  
      current_module = sys.modules[__name__]
  
      # If we're running from _version.py .
      tag_url = getattr(current_module, 'svn_tag_url', None)
      
      # If we're running from versioneer.py .
      if tag_url is None:
          vcs_settings = getattr(current_module, 'vcs_settings', None)
          if vcs_settings is not None and \
             'svn' in vcs_settings and \
             'tag_url' in vcs_settings['svn']:
              tag_url = vcs_settings['svn']['tag_url']
  
      if tag_url is None:
          raise ValueError("Please define VCS-specific 'tag_url' setting for "
                           "'svn' within 'versioneer'.")
  
      svn_commands = ['svn']
      info_xml = run_command(svn_commands, ['ls', '--xml', tag_url], cwd=root)
  # TODO(dustin): This should raise an EnvironmentError upon failure.
      if info_xml is None:
          print("Error accessing Subversion for latest version.")
          return {}
  
      (releases, latest_revision) = svn_parse_tag_xml(info_xml)
  
      release_info = releases[latest_revision]
      release_name = release_info['name']
      versions = { 'default': release_name, 
                   'version': release_name, 
                   'full': release_name }
  
  # Examples of strings returned by Git.
  #
  #    versions["closest_tag"]
  #    versions["distance"]
  #    versions["short_revisionid"]
  #    versions["dirty"]
  #    versions["pep440"]
  #    versions["describe"]
  #    versions["default"]
  #    versions["dash_dirty"]
  #    versions["closest_tag_or_zero"]
  #    versions["dash_distance"]
  
      return versions
docs: Return a dictionary of values derived directly from the VCS. This is the
      third attempt to find information by get_versions().