Check memcached backend in Django (#2778)

Bail if using old memcached backend

install.sh

@@ -23,6 +23,7 @@ source install/check-minimum-requirements.sh
 source install/turn-things-off.sh
 source install/create-docker-volumes.sh
 source install/ensure-files-from-examples.sh
+source install/check-memcached-backend.sh
 source install/ensure-relay-credentials.sh
 source install/generate-secret-key.sh
 source install/update-docker-images.sh

install/check-memcached-backend.sh

@@ -0,0 +1,16 @@
+echo "${_group}Checking memcached backend ..."
+
+if grep -q "\.PyMemcacheCache" "$SENTRY_CONFIG_PY"; then
+  echo "PyMemcacheCache found in $SENTRY_CONFIG_PY, gonna assume you're good."
+else
+  if grep -q "\.MemcachedCache" "$SENTRY_CONFIG_PY"; then
+    echo "MemcachedCache found in $SENTRY_CONFIG_PY, you should switch to PyMemcacheCache."
+    echo "See:"
+    echo "  https://develop.sentry.dev/self-hosted/releases/#breaking-changes"
+    exit 1
+  else
+    echo 'Your setup looks weird. Good luck.'
+  fi
+fi
+
+echo "${_endgroup}"