lxml is reporting "<string>:0:0:ERROR:XSLT:ERR_OK: unknown error“ when it should not.

[Rainer Hörbe]

Style sheets generated from schematron do not work until they are reformatted with Oxygen.

Python : sys.version_info(major=3, minor=4, micro=4, releaselevel='final', serial=0)
lxml.etree : (3, 6, 0, 0)
libxml used : (2, 9, 2)
libxml compiled : (2, 9, 2)
libxslt used : (1, 1, 28)
libxslt compiled : (1, 1, 28)

import lxml.etree as etree
transform = etree.XSLT(etree.parse('rules/schtron/rule02W.xsl'))
md_dom = etree.parse('testdata/rule02W_fail.xml')
out_dom = transform(md_dom)
print(transform.error_log.last_error)
<string>:0:0:ERROR:XSLT:ERR_OK: unknown error

workaround:

Details description and test data here:
https://github.com/rhoerbe/lxml-bug

[scoder (scoder)]

It's difficult to find the "most appropriate" error in XSLT output, because what libxslt generates is often not very informative.
PR welcome that improves the selectivity specifically for reported XSLT errors.