update train.py class count assertion #424

train.py

@@ -164,7 +164,7 @@ def train(hyp):
                                             hyp=hyp, augment=True, cache=opt.cache_images, rect=opt.rect)
     mlc = np.concatenate(dataset.labels, 0)[:, 0].max()  # max label class
     nb = len(dataloader)  # number of batches
-    assert mlc < nc, 'Label class %g exceeds nc=%g in %s. Correct your labels or your model.' % (mlc, nc, opt.cfg)
+    assert mlc < nc, 'Label class %g exceeds nc=%g in %s. Possible class labels are 0-%g' % (mlc, nc, opt.cfg, nc - 1)
 
     # Testloader
     testloader = create_dataloader(test_path, imgsz_test, batch_size, gs, opt,