mtest: fix flake8 issues
mtest: fix flake8 issues

jpakkane/meson,QuLogic/meson,pexip/meson,jpakkane/meson,pexip/meson,QuLogic/meson,QuLogic/meson,jpakkane/meson,QuLogic/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,mesonbuild/meson,pexip/meson,jpakkane/meson,pexip/meson,QuLogic/meson,mesonbuild/meson,QuLogic/meson,mesonbuild/meson,jpakkane/meson,QuLogic/meson,mesonbuild/meson,QuLogic/meson,QuLogic/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,mesonbuild/meson,jpakkane/meson,pexip/meson,jpakkane/meson,pexip/meson,pexip/meson,pexip/meson,pexip/meson,pexip/meson