Changelog for #2916

Author: JonRowe

Changelog.md

@@ -50,6 +50,8 @@ Bug fixes:
   (Zinovyev Ivan, #2903)
 * Fix `inspect` output of `RSpec::Core::Example::Procsy` to namespace correctly.
   (Keiko Kaneko, #2915)
+* Ensure formatters not exposing `#output` will not crash duplicate check.
+  (@niceking, #2916)
 
 ### 3.10.1 / 2020-12-27
 [Full Changelog](http://github.com/rspec/rspec-core/compare/v3.10.0...v3.10.1)