KeyError when handling errors

[chimezie]

When I hit an error in an XSL transform, amara triggers a KeyError while attempting to handle the error, giving the following traceback:

File "/Library/Python/2.6/site-packages/amara/xslt/tree/attribute_types.py", line 457, in prepare
col=element.columnNumber, msg=str(error))
File "/Library/Python/2.6/site-packages/amara/init.py", line 29, in init
message %= kwds
KeyError: 'text'