You can not override these warnings. Depending on your data, you might be able to ignore these warnings. See issue 273. In general, I would strongly discourage using PAR/REC and export to DICOM. If you have issues, you may want to look at these pages:
  https://github.com/xiangruili/dicm2nii
  https://github.com/nipy/nibabel/blob/master/nibabel/cmdline/parrec2nii.py
  https://github.com/rordenlab/dcm2niix/tree/master/PARREC
I do not have access to Philips hardware, so please validate carefully. I have not touched that code in a while, and it is an undocumented Philips research format that they have historically modified at will. My software does patch several known bugs from prior Philips releases, but these kludges may have unintended consequences.