Checkmk Werk 15495: Fix generation of report preview in background job

ID: 15495 Title: Fix generation of report preview in background job Component: Reporting & Availability Level: 1 Class: Bug fix Version: 2.1.0p30 If you used "Generate report preview in background job" on the report scheduler page, the background job failed with an error like "Exception: content argument must be Text, not bytes".