Restrict PyNaCL to 1.4.x on RHEL8 when using Python 3.6 (#4006)

* Restrict PyNaCL to 1.4.x on RHEL8 when using Python 3.6.

* Fix typo.

tests/utils/shippable/remote.sh

@@ -17,6 +17,10 @@ fi
 stage="${S:-prod}"
 provider="${P:-default}"
 
+if [ "${platform}" == "rhel" ] && [[ "${version}" =~ ^8 ]]; then
+    echo "pynacl >= 1.4.0, < 1.5.0; python_version == '3.6'" >> tests/utils/constraints.txt
+fi
+
 # shellcheck disable=SC2086
 ansible-test integration --color -v --retry-on-error "${target}" ${COVERAGE:+"$COVERAGE"} ${CHANGED:+"$CHANGED"} ${UNSTABLE:+"$UNSTABLE"} \
     --remote "${platform}/${version}" --remote-terminate always --remote-stage "${stage}" --remote-provider "${provider}"