enable rhel8 beta for testing in ec2 (#48831)

test/runner/completion/remote.txt

@@ -1,3 +1,4 @@
 freebsd/11.1
 osx/10.11
 rhel/7.6
+rhel/8.0

test/runner/setup/remote.sh

@@ -27,6 +27,33 @@ if [ "${platform}" = "freebsd" ]; then
 
     pip --version 2>/dev/null || curl --silent --show-error https://bootstrap.pypa.io/get-pip.py | python
 elif [ "${platform}" = "rhel" ]; then
+    if grep '8\.' /etc/redhat-release; then
+        while true; do
+            curl -o /etc/yum.repos.d/rhel-8-beta.repo http://downloads.redhat.com/redhat/rhel/rhel-8-beta/rhel-8-beta.repo && \
+            dnf config-manager --set-enabled rhel-8-for-x86_64-baseos-beta-rpms && \
+            dnf config-manager --set-enabled rhel-8-for-x86_64-appstream-beta-rpms && \
+            yum -y module install python36 && \
+            yum install -y \
+                gcc \
+                python3-devel \
+                python3-jinja2 \
+                python3-virtualenv \
+                python3-cryptography \
+                iptables \
+             && break
+             echo "Failed to install packages. Sleeping before trying again..."
+             sleep 10
+        done
+
+        # When running from source our python shebang is: #!/usr/bin/env python
+        # To avoid modifying all of our scripts while running tests we make sure `python` is in our PATH.
+        if [ ! -f /usr/bin/python ]; then
+            ln -s /usr/bin/python3 /usr/bin/python
+        fi
+        if [ ! -f /usr/bin/pip ]; then
+            ln -s /usr/bin/pip3 /usr/bin/pip
+        fi
+    else
         while true; do
             yum install -y \
                 gcc \
@@ -41,6 +68,7 @@ elif [ "${platform}" = "rhel" ]; then
 
         pip --version 2>/dev/null || curl --silent --show-error https://bootstrap.pypa.io/get-pip.py | python
     fi
+fi
 
 if [ "${platform}" = "freebsd" ] || [ "${platform}" = "osx" ]; then
     pip install virtualenv