fix installation of the latest pip for Python 2 in CentOS 7.9 container

centos-7.9/Dockerfile

@@ -4,4 +4,4 @@ RUN yum -y install epel-release && yum -y install python python2-pip Lmod
 RUN yum -y install bzip2 curl diffutils file gcc-c++ git gzip make openssl openssl-devel rdma-core-devel patch sudo tar unzip which xz
 RUN yum -y update ca-certificates
 # In order to install archspec we need to upgrade pip to latest version for Python 2
-RUN python -m pip install --upgrade 'pip<21' && python -m pip install archspec
+RUN python -m pip install --trusted-host pypi.python.org --trusted-host files.pythonhosted.org --trusted-host pypi.org --upgrade 'pip<21' && python -m pip install archspec