Replace mb_chars.limit with truncate_bytes in format_sync_error

app/models/manageiq/providers/embedded_ansible/automation_manager/configuration_script_source.rb

@@ -56,7 +56,7 @@ def format_sync_error(error)
     result = error.message.dup
     result << "\n\n"
     result << error.backtrace.join("\n")
-    result.mb_chars.limit(ERROR_MAX_SIZE)
+    result.truncate_bytes(ERROR_MAX_SIZE, :omission => nil)
   end
 
   private

spec/models/manageiq/providers/embedded_ansible/automation_manager/configuration_script_source_spec.rb

@@ -566,4 +566,25 @@ def notification_args(action, op_arg = params)
       expect(GitRepository.first.authentication).to be_nil
     end
   end
+
+  describe "#format_sync_error" do
+    let(:source) { FactoryBot.create(:embedded_ansible_configuration_script_source) }
+
+    it "returns the error message and backtrace joined together" do
+      error = RuntimeError.new("something went wrong")
+      allow(error).to receive(:backtrace).and_return(%w[line1 line2])
+
+      expect(source.format_sync_error(error)).to eq("something went wrong\n\nline1\nline2")
+    end
+
+    it "truncates the result to ERROR_MAX_SIZE bytes" do
+      error = RuntimeError.new("big error")
+      allow(error).to receive(:backtrace).and_return(["x" * 1024] * 100)
+
+      result = source.format_sync_error(error)
+
+      expect(result.bytesize).to be <= described_class::ERROR_MAX_SIZE
+      expect(result).to be_valid_encoding
+    end
+  end
 end