no sentry noise on malformed gradebook imports

closes FOO-1328
flag=none

TEST PLAN:
  1) upload a badly encoded file for gradebook
  2) the job should fail, as it already does,
     but without notifying sentry (logs still happen)

Change-Id: I3b09f93a2138bd843e0229bf25e15f54593879b7
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/255081
Reviewed-by: Rob Orton <rob@instructure.com>
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
QA-Review: Ethan Vizitei <evizitei@instructure.com>
Product-Review: Ethan Vizitei <evizitei@instructure.com>

lib/gradebook_importer.rb

@@ -52,6 +52,11 @@ class GradebookImporter
 
   def self.create_from(progress, gradebook_upload, user, attachment)
     self.new(gradebook_upload, attachment, user, progress).parse!
+  rescue CSV::MalformedCSVError => e
+    Canvas::Errors.capture_exception(:gradebook_import, e, :info)
+    # this isn't actually "retryable", but this error will make sure
+    # the job is marked "failed" without generating alarm noise.
+    raise Delayed::RetriableError, "Gradebook import did not parse cleanly"
   end
 
   def initialize(upload=nil, attachment=nil, user=nil, progress=nil)

spec/fixtures/gradebooks/wat.csv

@@ -0,0 +1,6 @@
+"1,asdf,fdsa \"rew qwer q\" ljhg,zxcv"
+ ✂ <20> 
+<xml>
+  <value>I'm not actually a csv!</value>
+</xml>
+qwerqqwerqwer,qwerq,wer,qwz,xcvz;;fjbnsaba;skdfj;as,asdf

spec/lib/gradebook_importer_spec.rb

@@ -89,6 +89,16 @@ describe GradebookImporter do
       expect(@gi.students.length).to eq 2
     end
 
+    it "expects and deals with invalid upload files" do
+      user = user_model
+      progress = Progress.create!(tag: "test", context: @user)
+      upload = GradebookUpload.new
+      upload = GradebookUpload.create!(course: gradebook_course, user: gradebook_user, progress: progress)
+      expect do
+        GradebookImporter.create_from(progress, upload, user, invalid_gradebook_contents)
+      end.to raise_error(Delayed::RetriableError)
+    end
+
     context 'when dealing with a file containing semicolon field separators' do
       context 'with interspersed commas to throw you off' do
         before(:each) do
@@ -1743,6 +1753,10 @@ describe GradebookImporter do
     attachment_with_file(File.join(File.dirname(__FILE__), %w(.. fixtures gradebooks basic_course_with_sis_login_id.csv)))
   end
 
+  def invalid_gradebook_contents
+    attachment_with_file(File.join(File.dirname(__FILE__), %w(.. fixtures gradebooks wat.csv)))
+  end
+
   def attachment_with
     a = attachment_model
     file = Tempfile.new("gradebook_import.csv")