Fix rpm artifact building: idna-3.1 doesn't support python-2 (in centos7-image.docker)
diff --git a/docker/centos7-image.docker b/docker/centos7-image.docker
index 7116449..ac8b1f6 100644
--- a/docker/centos7-image.docker
+++ b/docker/centos7-image.docker
@@ -33,7 +33,7 @@
# install ssl enabled urllib for retrieving python packages
# this will produce some ssl related warnings, which will be resolved once the package has been installed
-RUN pip install urllib3[secure]
+RUN pip install 'idna<3' urllib3[secure]
# upgrade to modern pip version
RUN pip install --upgrade pip
