ci: Prefer pip3 to install unit test dependencies.
While it looks like the right python3 versions of those dependencies
seems to be installed in the CI, prefer calling this via pip3 like the
rest of the script.
Fixes: ("python: Introduce unit tests.")
@@ -43,7 +43,7 @@ if [ "$M32" ]; then
fi
# Install python test dependencies
-pip install -r python/test_requirements.txt
+pip3 install -r python/test_requirements.txt
# IPv6 is supported by kernel but disabled in TravisCI images:
# https://github.com/travis-ci/travis-ci/issues/8891
