make sure strings don't sneak into bulk imports

closes FOO-1366
flag=none

TEST PLAN:
  1) run sis enrollments import that adds a string error
     to "messages"
  2) it gets inserted as a SisBatchError, no explosion

Change-Id: I87f54f5300448c5ed005612c44639d33bc4d41c7
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/255603
Tested-by: Service Cloud Jenkins <[email protected]>
Reviewed-by: Simon Williams <[email protected]>
QA-Review: Simon Williams <[email protected]>
Product-Review: Simon Williams <[email protected]>

lib/sis/csv/enrollment_importer.rb

@@ -44,10 +44,17 @@ def process(csv, index=nil, count=nil)
             end
           end
         end
-        SisBatch.bulk_insert_sis_errors(messages)
+        persist_errors(csv, messages, @batch)
         count
       end
 
+      def persist_errors(csv, messages, batch)
+        errors = messages.map do |message|
+          (message.is_a? SisBatchError) ? message : SisBatch.build_error(csv, message, sis_batch: @batch)
+        end
+        SisBatch.bulk_insert_sis_errors(errors)
+      end
+
       private
       def create_enrollment(row, messages, csv: nil)
         enrollment = SIS::Models::Enrollment.new(

spec/lib/sis/csv/enrollment_importer_spec.rb

@@ -623,6 +623,16 @@
     )
   end
 
+  describe "#persist_errors" do
+    it "gracefully handles string errors" do
+      batch = Account.default.sis_batches.create!
+      csv = double(root_account: Account.default, batch: batch, :[] => nil)
+      importer = SIS::CSV::EnrollmentImporter.new(csv)
+      importer.persist_errors(csv, ['a string error message'], batch)
+      expect(batch.sis_batch_errors.count).to eq(1)
+    end
+  end
+
   it 'should only queue up one recache_grade_distribution job per course' do
     Course.create!(account: @account, sis_source_id: 'C001', workflow_state: 'available')
     user_with_managed_pseudonym(account: @account, sis_user_id: 'U001')