[ScanBase] add get_relative_file

latest
Status Name Job ID Coverage
  Build
failed check_style #258247

failed check_style #258168

 
  Test
skipped test:python3.7_stretch_pyqt5 #258169
skipped test:python3.9_stretch_pyqt5 #258170
skipped test:test-tomoscan-tutorials #258171
 
Name Stage Failure
failed
check_style Build There has been a timeout failure or the job got stuck. Check your timeout limits or try again
No job log