issue2551142 - Import of retired node ... unique constraint failure. Title: Import of retired node with username after active node fails with unique constraint failure. More fixes needed for mysql and postgresql. mysql: add unique constraint for (keyvalue, __retired__) when creating class in the database. On schema change if class is changed, remove the unique constraint too. upgrade version of rdbms database from 5 to 6 to add constraint to all version 5 databases that were created as version 5 and didn't get the unique constraint. Make no changes on version 5 databases upgraded from version 4, the upgrade process to 5 added the constraint. Make no changes to other databases (sqlite, postgres) during upgrade from version 5 to 6. postgres: Handle the exception raised on unique constraint violation. The exception invalidates the database connection so it can't be used to recover from the exception. Added two new database methods: checkpoint_data - performs a db.commit under postgres does nothing on other backends restore_connection_on_error - does a db.rollback on postgres, does nothing on other backends with the rollback() done on the connection I can use the database connection to fixup the import that failed on the unique constraint. This makes postgres slower but without the commit after every imported object, the rollback will delete all the entries done up to this point. Trying to figure out how to make the caller do_import batch and recover from this failure is beyond me. Also dismissed having to process the export csv file before importing. Pushing that onto a user just seems wrong. Also since import/export isn't frequently done the lack of surprise on having a failing import and reduced load/frustration for the user seems worth it. Also the import can be run in verbose mode where it prints out a row as it is processed, so it may take a while, ut the user can get feedback. db_test-base.py: add test for upgrade from 5 to 6.

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Roundup Tracker Templates
=========================

The templates distributed with Roundup are stored in the "share" directory
nominated by Python. On Unix this is typically
``/usr/share/roundup/templates/`` (or ``/usr/local/share...``) and
on Windows this is ``c:\python22\share\roundup\templates\``.

The template loading looks in four places to find the templates:

1. *share* - eg. ``<prefix>/share/roundup/templates/*``.
   This should be the standard place to find them when Roundup is
   installed.
2. ``<roundup.admin.__file__>/../templates/*``.
   This will be used if Roundup's run in the distro (aka. source)
   directory.
3. ``<current working dir>/*``.
   This is for when someone unpacks a 3rd-party template.
4. ``<current working dir>``.
   This is for someone who "cd"s to the 3rd-party template dir.

Templates contain:

- modules ``schema.py`` and ``initial_data.py``
- directories ``html``, ``detectors`` and ``extensions``
  (with appropriate contents)
- optional ``config_ini.ini`` file. It is structured like a tracker's
  ``config.ini`` but contains only headers (e.g. ``[main]``) and
  *required* parameters that are different from defaults:
  e.g. ``template_engine = jinja2`` and ``static_files =
  static``. These settings override the default values saved to the
  tracker's ``config.ini``.
- template "marker" file ``TEMPLATE-INFO.txt``, which contains
  the name of the template, a description of the template
  and its intended audience.

An example TEMPLATE-INFO.txt::

 Name: classic
 Description: This is a generic issue tracker that may be used to track bugs,
              feature requests, project issues or any number of other types
              of issues. Most users of Roundup will find that this template
              suits them, with perhaps a few customisations.
 Intended-For: All first-time Roundup users