DEV: Log error backtrace in `Discourse.warn_exception` without logster.

DEV: Log error backtrace in Discourse.warn_exception without logster.

diff --git a/lib/discourse.rb b/lib/discourse.rb
index 67ac64c..9a5247d 100644
--- a/lib/discourse.rb
+++ b/lib/discourse.rb
@@ -745,7 +745,7 @@ module Discourse
       )
     else
       # no logster ... fallback
-      Rails.logger.warn("#{message} #{e}")
+      Rails.logger.warn("#{message} #{e}\n#{e.backtrace.join("\n")}")
     end
   rescue
     STDERR.puts "Failed to report exception #{e} #{message}"

GitHub sha: 531eca98