euca2ools's display_error_and_exit function determines whether or not an exception's message is XML by looking for a "<" character. When I ran euca-describe-images its call to get_all_images threw a SAXParseException (the cause of which was probably my fault and irrelevant to this bug.) The stringified version of the exception passed this check but wasn't XML, making display_error_and_exit's call to minidom.parseString throw an uncaught exception and making the program print a backtrace instead of an error message.
In my case, the variable ex near the very bottom of euca-describe-images yielded the following strings that illustrate the problem:
``repr(ex)'' yields ``SAXParseException('no element found',)''
``'%s' % ex'' yields ``<unknown>:1:0: no element found''
I propose changing the check for XML-ness on __init__.py lines 1071 and 1072 to something that checks the beginning and end of error messages so we are more likely to get useful output instead of backtraces when things go wrong. Perhaps even something along the lines of ``if ex.__str__().strip().startswith('<') && ex.__str__().strip().endswith('>')'' would be more robust than just assuming that anything with a '<' character is always XML.
This is a euca2ools issue.