[Satellite 6] Login to satellite with LDAP user fails with error "Oops, we're sorry but something went wrong / undefined method `each' for nil:NilClass"

Environment

• Red Hat Satellite 6 or Proxy 6.1/6.2
• LDAP

Issue

• When trying to login satellite webui with LDAP user it fails with error:

Oops, we're sorry but something went wrong
undefined method `each' for nil:NilClass
If you feel this is an error with Satellite 6 itself, please open a new issue with Satellite ticketing system, You would probably need to attach the Full trace and relevant log entries.
NoMethodError
undefined method `each' for nil:NilClass
app/models/auth_sources/auth_source_ldap.rb:103:in `update_usergroups'
app/models/user.rb:197:in `block in try_to_login'
app/models/concerns/foreman/thread_session.rb:73:in `as'
app/models/concerns/foreman/thread_session.rb:79:in `as_anonymous_admin'
app/models/user.rb:191:in `try_to_login'
app/controllers/users_controller.rb:71:in `login'
app/models/concerns/foreman/thread_session.rb:33:in `clear_thread'
lib/middleware/catch_json_parse_errors.rb:9:in `call'

Resolution

• Possible issue between the LDAP settings in Satellite 6.x and the LDAP server. Confirm that the Satellite LDAP groups and the groups on LDAP server match each other.
• Check attribute on LDAP server whether it have reached limit.

For more KB articles/solutions related to Red Hat Satellite 6.x Authentication Issues, please refer to the Red Hat Satellite Consolidated Troubleshooting Article for Red Hat Satellite 6.x Authentication Issues

Root Cause

• LDAP server was not functioning properly due to an attribute that had reached limit.

Diagnostic Steps

• Entries seen in /var/log/foreman/production.log file on satellite server:

16-03-28 10:07:30 [I] Completed 200 OK in 17ms (Views: 4.0ms | ActiveRecord: 0.0ms)
2016-03-28 10:07:30 [I] Processing by Katello::Api::Rhsm::CandlepinProxiesController#get as JSON
2016-03-28 10:07:30 [I]   Parameters: {"id"=>"xxxxx-f0d3-486c-92eb-xxxxxxx"}
2016-03-28 10:07:30 [I] Processing by UsersController#login as HTML
2016-03-28 10:07:30 [I]   Rendered users/login.html.erb within layouts/login (2.1ms)
2016-03-28 10:07:30 [I]   Rendered layouts/base.html.erb (1.3ms)
2016-03-28 10:07:30 [I] Completed 200 OK in 6ms (Views: 4.5ms | ActiveRecord: 0.0ms)
2016-03-28 10:07:30 [I] Completed 200 OK in 40ms (Views: 0.2ms | ActiveRecord: 0.0ms)
2016-03-28 10:07:30 [I] Processing by Katello::Api::Rhsm::CandlepinProxiesController#get as JSON
2016-03-28 10:07:30 [I]   Parameters: {"id"=>"xxxxx-f0d3-486c-92eb-xxxxxxx"}
2016-03-28 10:07:30 [I] Completed 200 OK in 51ms (Views: 0.2ms | ActiveRecord: 0.0ms)
2016-03-28 10:07:33 [I] Processing by UsersController#login as HTML
2016-03-28 10:07:33 [I]   Parameters: {"utf8"=>"✓", "authenticity_token"=>"RpPRqC7taJKxii1HEFiskfoDRNTHA24kGmMDP695lpdavE=", "login"=>{"login"=>"user1", "password"=>"[FILTERED]"}, "commit"=>"Login"}
2016-03-28 10:07:33 [I] Expire fragment views/tabs_and_title_records-19 (0.1ms)
2016-03-28 10:07:34 [W] Operation FAILED: undefined method `each' for nil:NilClass
2016-03-28 10:07:34 [I]   Rendered common/500.html.erb within layouts/application (4.1ms)
2016-03-28 10:07:34 [I]   Rendered layouts/base.html.erb (1.2ms)
2016-03-28 10:07:34 [I] Completed 500 Internal Server Error in 405ms (Views: 7.1ms | ActiveRecord: 3.4ms)

• Debug level logs:

logger.debug "Updating user groups for user #{login}"
    internal = User.find_by_login(login).external_usergroups.map(&:name)
    external = ldap_con.group_list(login) # this list may return all groups in lowercase
    (internal | external).each do |name|
      begin

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