Add a warning about bundle update to TROUBLESHOOTING.md

docs/TROUBLESHOOTING.md

@@ -21,27 +21,32 @@ reaching out to the community for help:
    We frequently update our dependencies to newer versions. It is a good idea to run
    `bundle install` every time you check out Discourse, especially if it's been a while.
 
+4. Did you run `bundle update`?
 
-3. Have you migrated your database?
+   Don't. Running `bundle update` will download gem versions that we haven't tested with.
+   The Gemfile.lock has the gem versions that Discourse currently uses, so `bundle install`
+   will work.  If you ran update, then you should uninstall the gems and run `bundle install`.
+
+5. Have you migrated your database?
 
    Our schema changes fairly frequently. After checking out the source code, you should 
    run `rake db:migrate`
 
 
-4. Have you added the seed data?
+6. Have you added the seed data?
 
    We depend on some basic seed data being present in the database. You should run 
    `rake db:seed_fu` to keep your database in sync.
 
 
-5. Do the tests pass?
+7. Do the tests pass?
 
    If you are having other problems, it's useful to know if the test suite passes. You 
    can run it by first using `rake db:test:prepare` and then `rake spec`. If you 
    experience any failures, that's a bad sign! Our master branch should *always* pass 
    every test.
 
-6. Have you updated host_names in your database.yml?
+8. Have you updated host_names in your database.yml?
 
    If links in emails have localhost in them, then you are still using the default host_names
    value in database.yml.  Update it to use your site's host name(s).