cf push identity-fake-server
...
Bundle complete! 12 Gemfile dependencies, 10 gems now installed.
Gems in the groups development and test were not installed.
Bundled gems are installed into `/tmp/contents405955630/deps/0/vendor_bundle`
-----> Regenerating bundler binstubs...
**WARNING** Your Gemfile.lock was bundled with bundler 2.1.4, which is incompatible with the current bundler version (2.2.13).
**WARNING** Deleting "Bundled With" from the Gemfile.lock
Cleaning up the bundler cache.
and update gems.