Fix typo to show name in format string

Fixes a typo in the format string for a NameError on a duplicate name.

Description

Fix the NameError so that is says e.g.

'New POI name "my-name" already present in current POI list.'"

instead of

"'New POI name "{0}" already present in current POI list.'"

There's also an trailing newline at the end that the Github text editor added automatically.

This gives a more informative error message.

Trivial change, has been tested manually.

[x] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[ ] Breaking change (fix or feature that would cause existing functionality to not work as expected)

[x] My code follows the code style of this project.
[ ] I have documented my changes in the changelog (documentation/changelog.md)
[ ] My change requires a change to the documentation.
[ ] I have updated the documentation accordingly.
[ ] I have added/updated for the module the config example in the docstring of the class accordingly.
[x] I have checked that the change does not contain obvious errors (syntax, indentation, mutable default values).
[ ] I have tested my changes using 'Load all modules' on the default dummy configuration with my changes included.
[ ] All changed Jupyter notebooks have been stripped of their output cells.