CI: Install python3.8 on older distros

ci/centos-7/Dockerfile

@@ -39,9 +39,10 @@ RUN yum -y install \
     make \
     openssl \
     openssl-devel \
-    python3 \
-    python3-devel \
-    python3-pip\
+    rh-python38 \
+    rh-python38-devel \
+    rh-python38-python-devel \
+    rh-python38-pip \
     sqlite \
     swig \
     which \
@@ -59,6 +60,7 @@ RUN pip3 install websockets junit2html
 
 RUN echo 'unset BASH_ENV PROMPT_COMMAND ENV' > /usr/bin/zeek-ci-env && \
     echo 'source /opt/rh/devtoolset-8/enable' >> /usr/bin/zeek-ci-env && \
+    echo 'source /opt/rh/rh-python38/enable' >> /usr/bin/zeek-ci-env && \
     echo 'export PATH=${PATH}:${FLEX_DIR}/bin' >> /usr/bin/zeek-ci-env
 
 ENV BASH_ENV="/usr/bin/zeek-ci-env" \

ci/centos-stream-8/Dockerfile

@@ -21,9 +21,9 @@ RUN dnf -y install \
     openssl \
     openssl-devel \
     procps-ng \
-    python3 \
-    python3-devel \
-    python3-pip\
+    python38 \
+    python38-devel \
+    python38-pip\
     sqlite \
     swig \
     which \

ci/opensuse-leap-15.4/Dockerfile

@@ -19,15 +19,17 @@ RUN zypper addrepo https://download.opensuse.org/repositories/openSUSE:Leap:15.4
     libopenssl-devel \
     libpcap-devel \
     make \
-    python3 \
-    python3-devel \
-    python3-pip \
+    python39 \
+    python39-devel \
+    python39-pip \
     swig \
     tar \
     which \
     zlib-devel \
   && rm -rf /var/cache/zypp
 
+RUN update-alternatives --install /usr/bin/pip3 pip3 /usr/bin/pip3.9 100
+
 RUN pip3 install websockets junit2html
 
 RUN update-alternatives --install /usr/bin/cc cc /usr/bin/gcc-10 100