+if (!requireNamespace("XML")) {
+ # XML 3.99-0.4 depends on R >= 4.0.0, but we run tests on debian
+ # stable (10) with R 3.5.2 so we install an older version from
+ # source.
+ install.packages("https://cran.r-project.org/src/contrib/Archive/XML/XML_3.99-0.3.tar.gz", repos=NULL, type="source")
+}