Univention Corporate Server 4.0 erratum 18 (bugfix)

* The notification while changing objects which are part of an Active
  Directory domain has been placed in a more visible area.
* The error message if the connection to the LDAP server fails
  has been extended.
* The UMCP command udm/layout failed if a DN was given which could not
  be identified as UDM object.
* The get_exception_method has been removed. Error information are now
  provided by the UDM base exception itself.
* Exceptions are not re-raised anymore as this hides important error
  information in traceback feedback reports.
* After changing the own password a login dialog is shown if a LDAP
  connection needs to be reestablished.
* It is now prevented that a search with a given attribute name can raise
  a bad search filter exception.
* The search form does not allow invalid values to be submitted anymore.
* Users without POSIX option are now able to use the UMC module.
* An error message is now shown when trying to operations on non existing
  objects.
* Searching for an invalid object type will not raise an exception
  anymore.
* Opening a nonexistent object (e.g. object was moved / deleted)
  now shows an error message instead of raising an exception.
* Automatic IP assignment for a network will show an error message if there
  is no more IP available to use instead of a traceback.
* A Free for personal use license can now be imported via the UMC module
  without specifying the LDAP base.
* Error handling has been improved in case a UDM module could not be
  identified.