Message severity from XSLT messages

[josteinaj]

I don't think there's a way to signal a message severity from the XSLT xsl:message step (except for terminate="yes|no".

Either:

• we need some mechanism like for instance our own implementation of xsl:message that supports severities,
• or we just allow messages to begin with a [WARNING], [DEBUG] etc. string as is already done in some places in the code, and leave it up to the
  • the engine should then preferably parse these strings
  • alternatively the client library will have to do so, which is less ideal

[bertfrees]

Fixed by daisy/pipeline-modules@80ce8b0