Comment 2 for bug 1642950

I can reproduce, with configuration (on Windows 10, Cygwin):

Python : sys.version_info(major=2, minor=7, micro=13, releaselevel='final', serial=0)
lxml.etree : (3, 7, 3, 0)
libxml used : (2, 9, 4)
libxml compiled : (2, 9, 4)
libxslt used : (1, 1, 29)
libxslt compiled : (1, 1, 29)

Furthermore, the following suggests the problem is on the validation side, not etree as such:

>>> x=etree.parse("testa.xml")
>>> x.root().attrib['foo']
'true'