Leapp upgrade fails with error message "ImportError: No module named ipaddress"

Issue

Leapp upgrade failes with following error:

Traceback (most recent call last):
  File "/usr/lib64/python2.7/multiprocessing/process.py", line 258, in _bootstrap
    self.run()
  File "/usr/lib64/python2.7/multiprocessing/process.py", line 114, in run
    self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.7/site-packages/leapp/repository/actor_definition.py", line 31, in inspect_actor
    definition.load()
  File "/usr/lib/python2.7/site-packages/leapp/repository/actor_definition.py", line 196, in load
    self._module = importer.find_module(name).load_module(name)
  File "/usr/lib64/python2.7/pkgutil.py", line 246, in load_module
    mod = imp.load_module(fullname, self.file, self.filename, self.etc)
  File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/migratesendmail/actor.py", line 5, in <module>
    from leapp.libraries.actor import migratesendmail
  File "/usr/lib64/python2.7/pkgutil.py", line 246, in load_module
    mod = imp.load_module(fullname, self.file, self.filename, self.etc)
  File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/migratesendmail/libraries/migratesendmail.py", line 1, in <module>
    import ipaddress
ImportError: No module named ipaddress