Can't submit a job with dependencies

[donalm]

When I try to submit a job with two layers, with either a frame or layer dependency I get this error:

Failed to parse job spec XML, org.jdom.input.JDOMParseException: Error on line 1: Attribute value "b'False'" of type NMTOKEN must be a name token.

A bit of digging reveals that the XML fragment received by Cuebot has a problem:

<depends>
  <depend anyframe="b'False'" type="LAYER_ON_LAYER">
    <depjob>b858be71-6467-4e00-997a-824b32fb0e0c</depjob
    <deplayer>MyTaskNameTwoB</deplayer>
    <onjob>b858be71-6467-4e00-997a-824b32fb0e0c</onjob>
    <onlayer>MyTaskNameOneA</onlayer>
  </depend>
</depends>

The 'anyframe' value is added in the build_dependencies method in outline/backend/cue.py:

        depend = Et.SubElement(all_depends, "depend",                           
                               type=dep.get_type(),                             
                               anyframe=str(dep.is_any_frame()))

Looks innocuous, but str is imported from builtins, so it's of type future.types.newstr.newstr.

I guess xml.etree.ElementTree.SubElement is not happy with an newstr instance.