WSDL doesn't import exception namespaces

I'm attempting to get Crowd to work with the Python ZSI code-generation facilities. However when running wsdl2py on the Crowd WSDL I get the following error:

ZSI.generate.Wsdl2PythonError: No built-in typecode for type definition("http://exception.integration.crowd.atlassian.com","InvalidAuthorizationTokenException"): <schema targetNamespace="urn:SecurityServer"><element name="InvalidAuthorizationTokenException">

This appears to be because the exception namespaces are not imported. Adding the lines:

<xsd:import namespace="http://exception.integration.crowd.atlassian.com"/>
<xsd:import namespace="http://rmi.java"/>

to the urn:SecurityServer schema appears to fix this.