Calabash implements a few extension attributes on standard steps.
These attributes are in the “Calabash extension namespace”, http://xmlcalabash.com/ns/extensions, identified by the prefix “cx”.
The cx:show-stderr extension attribute (introduced in XML Calabash 0.9.2) controls whether or not process output to STDERR is displayed as the process runs. It defaults to true.
If errors-is-xml is true, this extension attribute is ignored.