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Update all logger.warn calls to logger.warning as warn is obsolete.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

Don't use f string yet

See merge request !116

The processing nodes are not on Python 3.6 yet
therefore these can not be used.

The other uses are only related to tests and
tasks not done on the processing nodes.

Only enable GPU runtime if available

See merge request !115

Some execution environments may run CPU as well as GPU
code, this check for Nvidia driver presence will allow
to reuse the same environment on both.

It also updates the GPU option to use the latest version
provided by the nvidia-docker2 documentation.

Improve execution handling

See merge request !114

This avoids accidental writes in the container that
will be lost anyway.

When starting a docker container, use the same user as the one
currently executing the code if nothing else has been put in
the configuration. This allows to have consistent access across
executions.

Add missing variable initialisation for optional argument in worker script

See merge request !113

Improve disconnection handling

See merge request !112

improve complex setup handling

See merge request !111

Support giving a custom mount point to use for volume setup.

This will replace the cache path when creating the volumes.

Make cache access more specific

See merge request !110

It was not matching the one created by the original discovery
and thus fails to find the environments for the tests.

This will only mount what is needed by the various containers.

Improve handling of message handler shutdown in local executor

See merge request !109

Relates to beat.backend.python#30

Handle docker exception following the raise on error property for the new environment discovery

Closes #93

See merge request !108