I cannot find the XML expat module for python3.

On my system python3 is installed, including the packages "python3-pip",
"python-xml" and "python3-base". However, pip3 does not start because the xml
expat module is missing:

Traceback (most recent call last):
  File "/usr/bin/pip3", line 6, in <module>
    from pkg_resources import load_entry_point
  File "/usr/lib/python3.6/site-packages/pkg_resources/__init__.py", line 35,
in <module>
    import plistlib
  File "/usr/lib64/python3.6/plistlib.py", line 65, in <module>
    from xml.parsers.expat import ParserCreate
ModuleNotFoundError: No module named 'xml'

Also the command python3 -c "import xml" fails but python2 -c "import xml" is
woking.

Even if I just could not find the correct package which provides the xml
module, python3-pip should automatically pull the missing package in.