code: def open_scr(self):
          
          scr_path = self.scr_path
  
          if not scr_path:
              logger.critical("%s didn't produce a SCR.nc file in %s" % (self, self.outdir))
              return None
  
          # Open the GSR file and add its data to results.out
          from abipy.electrons.scr import ScrFile
          try:
              return ScrFile(scr_path)
          except Exception as exc:
              logger.critical("Exception while reading SCR file at %s:\n%s" % (scr_path, str(exc)))
              return None
docs: Open the SIGRES file located in the in self.outdir.
          Returns :class:`ScrFile` object, None if file could not be found or file is not readable.