CI: show skipped Python tests

Call pytest3 with argument -ra to display the reason why Python tests are
skipped.

The -r flag displays a test summary info for each test. -ra eliminates
this info for passed tests.

Pros an cons were discussed in:
https://lists.denx.de/pipermail/u-boot/2020-June/417090.html

Signed-off-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index a685a78..d074695 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -46,7 +46,7 @@
     # "${var:+"-k $var"}" expands to "" if $var is empty, "-k $var" if not
     - export PATH=/opt/qemu/bin:/tmp/uboot-test-hooks/bin:${PATH};
       export PYTHONPATH=/tmp/uboot-test-hooks/py/travis-ci;
-      ./test/py/test.py --bd ${TEST_PY_BD} ${TEST_PY_ID}
+      ./test/py/test.py -ra --bd ${TEST_PY_BD} ${TEST_PY_ID}
         ${TEST_PY_TEST_SPEC:+"-k ${TEST_PY_TEST_SPEC}"}
         --build-dir "$UBOOT_TRAVIS_BUILD_DIR"