Runtime: work around 1s delay added when using twisted reactor's callLater.

Since wxPython4, using wxReactor from non-main thread was producing
exceptions in wxWidget's C++ code. Then reactor.run() was called from
main thread, and runtime's worker was delegating calls to reactor
with callLater(0, callable).

While this worked perfectly with wxReactor, it did introduce an unexplained
1 second delay to each worker call when using nomal linux reactors
(i.e. without wxPython). As a workaround reactor runs in a thread when using
twisted without wxPython

image: skvorl/beremiz-requirements

pipelines:
  default:
    - parallel:
        - step:
            name: Codestyle checks
            script:
              - ln -s /CanFestival-3 $BITBUCKET_CLONE_DIR/../CanFestival-3
              - /usr/bin/python --version
              - ./tests/tools/check_source.sh
        - step:
            name: Application tests
            max-time: 10
            script:
              - ln -s /CanFestival-3 $BITBUCKET_CLONE_DIR/../CanFestival-3
              - ./tests/tools/run_python_tests.sh