[arekm@tarm ~]$ cat 123.py
import libxml2

doc = libxml2.newDoc('1.0')
epp_element = doc.newChild(None, "epp", None)
epp_element.newNs('aaaa', None)
xsi = epp_element.newNs('bbbb','xsi')
epp_element.setNsProp(xsi, "schemaLocation", 'ddddd')
command_element = epp_element.newChild(None,'command', None)
logout_element = command_element.newChild(None, 'logout', None)
clTRID_element = command_element.newChild(None, 'clTRID', '>')
print doc.serialize('UTF-8',  1)
doc.freeDoc()

[arekm@tarm ~]$ python 123.py
<?xml version="1.0" encoding="UTF-8"?>
<epp xmlns="aaaa" xmlns:xsi="bbbb" xsi:schemaLocation="ddddd">
  <command>
    <logout/>
    <clTRID>&gt;</clTRID>
  </command>
</epp>

[arekm@tarm ~]$ vim 123.py
[arekm@tarm ~]$ cat 123.py
import libxml2

doc = libxml2.newDoc('1.0')
epp_element = doc.newChild(None, "epp", None)
epp_element.newNs('aaaa', None)
xsi = epp_element.newNs('bbbb','xsi')
epp_element.setNsProp(xsi, "schemaLocation", 'ddddd')
command_element = epp_element.newChild(None,'command', None)
logout_element = command_element.newChild(None, 'logout', None)
clTRID_element = command_element.newChild(None, 'clTRID', '&')
print doc.serialize('UTF-8',  1)
doc.freeDoc()

[arekm@tarm ~]$ python 123.py
unterminated entity reference
<?xml version="1.0" encoding="UTF-8"?>
<epp xmlns="aaaa" xmlns:xsi="bbbb" xsi:schemaLocation="ddddd">
  <command>
    <logout/>
    <clTRID/>
  </command>
</epp>