Use libxml's structured error callback instead of vararg one

7 jobs for <span class="ref-name">err</span> in 25 minutes and 19 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #219378
fedora test

00:10:08

 
  Lint
manual #219380
allowed to fail manual
clippy
failed #219379
rustfmt

00:04:12

passed #219381
tarball

00:13:56

 
  Cross Distro
skipped #219384
debian_i386:testing
skipped #219383
debian:testing
skipped #219382
fedora:rawhide
 
Name Stage Failure
failed
rustfmt Lint
+        cstr(error.file),
+ error.line,
+ column,
+ cstr(error.message)
+ );
state.error(&full_error_message);
}

ERROR: Job failed: exit code 1