Wrap errors on GitHub importer to raise Projects::ImportService::Error

lib/gitlab/bitbucket_import/importer.rb

@@ -16,6 +16,8 @@ def execute
         import_issues if has_issues?
 
         true
+      rescue ActiveRecord::RecordInvalid => e
+        raise Projects::ImportService::Error.new, e.message
       ensure
         Gitlab::BitbucketImport::KeyDeleter.new(project).execute
       end

lib/gitlab/github_import/importer.rb

@@ -35,8 +35,8 @@ def import_issues
         end
 
         true
-      rescue ActiveRecord::RecordInvalid
-        false
+      rescue ActiveRecord::RecordInvalid => e
+        raise Projects::ImportService::Error, e.message
       end
 
       def import_pull_requests
@@ -53,8 +53,8 @@ def import_pull_requests
         end
 
         true
-      rescue ActiveRecord::RecordInvalid
-        false
+      rescue ActiveRecord::RecordInvalid => e
+        raise Projects::ImportService::Error, e.message
       end
 
       def import_comments(issue_number, noteable)
@@ -83,10 +83,13 @@ def import_wiki
 
         true
       rescue Gitlab::Shell::Error => e
-        if e.message =~ /repository not exported/
-          true
+        # GitHub error message when the wiki repo has not been created,
+        # this means that repo has wiki enabled, but have no pages. So,
+        # we can skip the import.
+        if e.message !~ /repository not exported/
+          raise Projects::ImportService::Error, e.message
         else
-          false
+          true
         end
       end
     end