Fix extracting workflows from purged and deleted histories

        """Return all active contents ordered by hid."""

        return self.contents_iter(types=["dataset", "dataset_collection"], deleted=False, visible=True)

    @property

    def visible_contents(self):

        return self.contents_iter(types=["dataset", "dataset_collection"], visible=True)

    def contents_iter(self, **kwds):

        """

        Fetch filtered list of contents of history.

        # just grab the implicitly mapped jobs and handle in second pass. Second pass is

        # needed because cannot allow selection of individual datasets from an implicit

        # mapping during extraction - you get the collection or nothing.

        for content in self.history.active_contents:

        for content in self.history.visible_contents:

            self.__summarize_content(content)

    def __summarize_content(self, content):

    <div class="warningmark">${warning}</div>

%endfor

<form method="post" action="${h.url_for(controller='workflow', action='build_from_current_history')}">

<form method="post" action="${h.url_for(controller='workflow', action='build_from_current_history', history_id=trans.security.encode_id(history.id))}">

<div class='form-row'>

    <label>Workflow name</label>

    <input name="workflow_name" type="text" value="Workflow constructed from history '${ util.unicodify( history.name )}'" size="60"/>

    def active_contents(self):

        return self.active_datasets

    @property

    def visible_contents(self):

        return self.active_contents

class MockTrans:

    def __init__(self, history):