Why Leapp fais with "OSError: [Errno 2] No such file or directory: 'sysctl'" ?

Issue

• leapp preupgrade fails with the error No such file or directory.

  ~~~
  Risk Factor: high (error)
  Title: Actor system_facts unexpectedly terminated with exit code: 1
  Summary: Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/leapp/repository/actor_definition.py", line 74, in _do_run
  actor_instance.run(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/leapp/actors/__init__.py", line 289, in run
  self.process(*args)
  File "/usr/share/leapp-repository/repositories/system_upgrade/common/actors/systemfacts/actor.py", line 53, in process
  self.produce(systemfacts.get_sysctls_status())
  File "/usr/share/leapp-repository/repositories/system_upgrade/common/actors/systemfacts/libraries/systemfacts.py", line 215, in get_sysctls_status
  return SysctlVariablesFacts(sysctl_variables=_get_sysctls())
  File "/usr/share/leapp-repository/repositories/system_upgrade/common/actors/systemfacts/libraries/systemfacts.py", line 41, in inner
  return list(f(*args, **kwargs))
  File "/usr/share/leapp-repository/repositories/system_upgrade/common/actors/systemfacts/libraries/systemfacts.py", line 188, in _get_sysctls
  for sc in run(['sysctl', '-a'], split=True)['stdout']:
  File "/usr/lib/python2.7/site-packages/leapp/libraries/stdlib/__init__.py", line 185, in run
  stdin=stdin, env=env, encoding=encoding)
  File "/usr/lib/python2.7/site-packages/leapp/libraries/stdlib/call.py", line 147, in _call
  raise OSError(errno.ENOENT, os.strerror(errno.ENOENT), command[0])
  OSError: [Errno 2] No such file or directory: 'sysctl'
  ~~~