The STRIDE execution step is skipped if no AlphaFold model file (.pdb extension) can be found

How to reproduce? Observed behaviour

STRIDE is only executed if AlphaFold model file (.pdb extension) can be found! Therefore Picnic only uses features from the sequence, which is ok, but we can not guarantee the accuracy. Please have a look at the following method.

def produce_stride_output_af(af_models_path, name, stride_out_path):

   forstride = os.listdir(af_models_path)
   result = [i for i in forstride if (i.startswith("AF-" + name + "-") and i.endswith(".pdb"))]
   for f in result:
      if f.endswith(".pdb"):
         pr.execSTRIDE(af_models_path + f, outputname=f, outputdir=stride_out_path)
   return

Expected behaviour

Exit with an appropiated error if no AlphaFold model file can be found in manual mode

cc: @soumyadeep.ghosh.consulting @hadarovi @tothpet