Acknowledge that --wls and --kurtdir flags can not both be set

unit_tests/fdt/dtifit/feedsRun

@@ -127,6 +127,9 @@ def fit_data(directory):
     for kurtdir in (False, True):
         for main_kurt in (False, True):
             for wls in (False, True):  # in this noise-free data the --wls flag should not matter
+                if wls and kurtdir:
+                    # weighted least square not implemented for kurtdir
+                    continue
                 cmd = [
                     'dtifit',
                     '-k', f'{directory}/ref_data.nii.gz',