Warn on QR Code generation if `baseurl` is not set

[oscarlevin]

I just implemented this in the CLI since I wanted to trigger a regeneration of qr codes when the baseurl was changed. This should probably be a warning from pretext/pretext though. @rbeezer, you can either close this or assign it to me if you don't or do agree.

[rbeezer]

Yes, it would be good to warn about not having this set. Folks might not be aware of the necessity. In the extraction stylesheet I would guess. LaTeX stylesheet might make sense, but static interactives are a broader thing than just LaTeX.

(Thanks vey much for the recent patrolling of stale issues.)

[ascholerChemeketa]

Just noticed this one...

I noticed the same thing and fixed in this PR:
#2676

It generates this:

<xsl:message>PTX:ERROR:   Base URL must be specified to generate QR codes</xsl:message>

@oscarlevin What does the CLI look for? Will anything with PTX:ERROR trigger fail logic in the CLI?

[oscarlevin]

The pretext/pretext xsltproc function sniffs for PTX:ERROR and similar in the output and logs them appropriately. I think this should probably be PTX:WARNING which will get logged as a warning but not cause a nonzero exit code. But maybe it should? I guess I don't feel strongly about the distinction (warning are easy to lose track of).

[rbeezer]

I like a warning when there is some reasonable default and things can proceed to an OK conclusion. If there is no base URL, what are you going to do? The QR codes will be worthless, no? Thus, the decision to make this an error.