Ensure that writing to a non existing output shows an error

See merge request !123

It has been the case for a while for beat/beat.backend.cxx>

- beat.env.python.tests 1.3.0r7
- beat.env.db.examples 1.4.0r7
- beat.env.cxx 2.0.0r4
- beat.env.cxxdev 2.0.0r4

Add optionnal environment entry to database

See merge request !122

This makes use of the new environment field that can be
added to the database declaration and is then used to
select the runtime environment in place of the database
search done until now.

This replaces the database name based search.

This field will allow to specify which environment should
be used to use a database. If not present, the old detection
process is used.

Fix database prototype

Closes #97

See merge request !121

This ensure that the setup call is properly done

Move to new images

See merge request !120

Add test assets with too long descriptions

See merge request !119

This will allow to improve tests also in beat/beat.cmdline>

Logger cleanup

See merge request !118

Update all logger.warn calls to logger.warning as warn is obsolete.

Also removes all unused logger instances.

Add size constraint for description field

Closes #95

See merge request !117

The max length matches the one from the database of beat/beat.web>