test-migrations: Add a check to avoid auto named migrations.

tools/test-migrations

@@ -1,6 +1,21 @@
 #!/bin/bash
 set -e
 echo 'Testing whether migrations are consistent with models'
+
+new_auto_named_migrations=$(./manage.py showmigrations | grep -v '0004_auto_20160423_0400\|0005_auto_20160727_2333\|0052_auto_fix_realmalias_realm_nullable\|0089_auto_20170710_1353' | grep "_auto_20")
+# We check if there is any new migration with the 'auto' keyword in its name and
+# cause a error to rename to a more meaningful name
+if [ "$new_auto_named_migrations" != "" ]; then
+    echo "ERROR: New migrations with unclear automatically generated names."
+    echo "Please rename these migrations to have readable names:"
+    echo
+    echo "$new_auto_named_migrations" | sed 's/\[[x ]\] /  /'
+    echo
+    echo 'See https://zulip.readthedocs.io/en/latest/schema-migrations.html for advice.'
+    echo
+    exit 1
+fi
+
 if ! ./manage.py makemigrations --check --dry-run; then
     echo
     echo 'ERROR: Migrations are not consistent with models!  Fix with `./tools/renumber-migrations`.'