Error 500 on SERVER: Server Error: Could not find class puppet_agent for mom.com on node mom.com

PROBLEM:
[root@MoM]# puppet agent -t
Info: Using configured environment 'production'
Info: Retrieving pluginfacts
Info: Retrieving plugin
Info: Retrieving locales
Info: Loading facts
Error: Could not retrieve catalog from remote server: Error 500 on SERVER: Server Error: Could not find class puppet_agent for mom.com on node mom.com
Warning: Not using cache on failed catalog
Error: Could not retrieve catalog; skipping run
SOLUTION:
Deploy the production environment.
puppet access login --service-url https://$(hostname -f):4433/rbac-api --lifetime 5d                              puppet code deploy production --wait
puppet agent -t

Also, make sure these lines are in Puppetfile:  

   mod 'puppetlabs-puppet_agent'

   mod 'puppetlabs-stdlib'