#3 User function argument validation is not occuring in the GUI.

[Edward d'Auvergne]

This can be seen when creating a data pipe in the GUI and then running the structure.read_pdb user function without arguments:

relax> pipe.create(pipe_name='validation_test', pipe_type='mf', bundle=None)

relax> structure.read_pdb(file=None, dir=None, read_mol=None, set_mol_name=None, read_model=None, set_model_num=None, alt_loc=None, verbosity=1, merge=False)
Traceback (most recent call last):
  File "/data/relax/relax/gui/interpreter.py", line 306, in run
    fn(*args, **kwds)
  File "/data/relax/relax/pipe_control/structure/main.py", line 1277, in read_pdb
    if not access(file_path, F_OK):
TypeError: coercing to Unicode: need string or buffer, NoneType found

Instead of this behaviour, relax should raise a RelaxError for the file argument being set to None.

[Edward d'Auvergne]

This has been fixed in commit 884acb06880845af98fa71a6772c0fe465b74907.