code: def get_invocation_command_nodefault(
      toolset, tool, user_provided_command=[], additional_paths=[], path_last=False):
      
      assert isinstance(toolset, basestring)
      assert isinstance(tool, basestring)
      assert is_iterable_typed(user_provided_command, basestring)
      assert is_iterable_typed(additional_paths, basestring) or additional_paths is None
      assert isinstance(path_last, (int, bool))
  
      if not user_provided_command:
          command = find_tool(tool, additional_paths, path_last)
          if not command and __debug_configuration:
              print "warning: toolset", toolset, "initialization: can't find tool, tool"
              #FIXME
              #print "warning: initialized from" [ errors.nearest-user-location ] ;
      else:
          command = check_tool(user_provided_command)
          if not command and __debug_configuration:
              print "warning: toolset", toolset, "initialization:"
              print "warning: can't find user-provided command", user_provided_command
              #FIXME
              #ECHO "warning: initialized from" [ errors.nearest-user-location ]
              command = []
          if command:
              command = ' '.join(command)
  
      return command
docs: A helper rule to get the command to invoke some tool. If
          'user-provided-command' is not given, tries to find binary named 'tool' in
          PATH and in the passed 'additional-path'. Otherwise, verifies that the first
          element of 'user-provided-command' is an existing program.
  
          This rule returns the command to be used when invoking the tool. If we can't
          find the tool, a warning is issued. If 'path-last' is specified, PATH is
          checked after 'additional-paths' when searching for 'tool'.