support/docker: add python3-pytest

... so the unit tests for check-package can run in the GitLab CI.

Signed-off-by: Ricardo Martincoski <ricardo.martincoski@gmail.com>
Acked-by: Romain Naour <romain.naour@smile.fr>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>

support/docker/Dockerfile

@@ -41,6 +41,7 @@ RUN apt-get install -y --no-install-recommends \
         python3-flake8 \
         python3-nose2 \
         python3-pexpect \
+        python3-pytest \
         qemu-system-arm \
         qemu-system-x86 \
         rsync \