I can reproduce this, and it seems to come from the serialiser. However, the serialisation happens in libxml2, not lxml. Worth investigating if this works with other libxml2 versions than 2.9.10. (There's a problem with 2.9.11/12 that prevents their use, 2.9.13 has an uncertain release date.)
I can reproduce this, and it seems to come from the serialiser. However, the serialisation happens in libxml2, not lxml. Worth investigating if this works with other libxml2 versions than 2.9.10. (There's a problem with 2.9.11/12 that prevents their use, 2.9.13 has an uncertain release date.)