[BB Importer] Save the error trace and the whole raw document

changelogs/unreleased/bb_save_trace.yml

+---
+title: "[BB Importer] Save the error trace and the whole raw document to debug problems
+  easier"
+merge_request:
+author:

lib/bitbucket/representation/base.rb

 module Bitbucket
   module Representation
     class Base
+      attr_reader :raw
+
       def initialize(raw)
         @raw = raw
       end
@@ -8,10 +10,6 @@ module Bitbucket
       def self.decorate(entries)
         entries.map { |entry| new(entry)}
       end
-
-      private
-
-      attr_reader :raw
     end
   end
 end

lib/gitlab/bitbucket_import/importer.rb

@@ -149,7 +149,7 @@ module Gitlab
             description += @formatter.author_line(pull_request.author) unless find_user_id(pull_request.author)
             description += pull_request.description
 
-            merge_request = project.merge_requests.create(
+            merge_request = project.merge_requests.create!(
               iid: pull_request.iid,
               title: pull_request.title,
               description: description,
@@ -168,7 +168,7 @@ module Gitlab
 
             import_pull_request_comments(pull_request, merge_request) if merge_request.persisted?
           rescue StandardError => e
-            errors << { type: :pull_request, iid: pull_request.iid, errors: e.message }
+            errors << { type: :pull_request, iid: pull_request.iid, errors: e.message, trace: e.backtrace.join("\n"), raw_response: pull_request.raw }
           end
         end
       end