WFS Service: error in get_schema if _get_remote_describefeaturetype returns exception XML

[brentfraser]

This should never happen where a layer is listed as existing in GetCapabilities, but has an error response when DescribeFeatureType is requested. Still, some servers can be mis-configured, and this can cause a crash in _get_schema at line 55 in schema.py:

    type_element = root.find("./{%s}element" % XS_NAMESPACE)
    complex_type = type_element.attrib["type"].split(":")[1]

The fix is to test for None:

    type_element = root.find("./{%s}element" % XS_NAMESPACE)
    if type_element is None:
        return None
    complex_type = type_element.attrib["type"].split(":")[1]