pycaffe: reorder exceptions

It doesn't make sense to complain about input not being batch-sized if
it isn't even 4-d in the first place.

python/caffe/pycaffe.py

@@ -57,10 +57,10 @@ def _Net_forward(self, blobs=None, **kwargs):
         # Set input according to defined shapes and make arrays single and
         # C-contiguous as Caffe expects.
         for in_, blob in kwargs.iteritems():
-            if blob.shape[0] != self.blobs[in_].num:
-                raise Exception('Input is not batch sized')
             if blob.ndim != 4:
                 raise Exception('{} blob is not 4-d'.format(in_))
+            if blob.shape[0] != self.blobs[in_].num:
+                raise Exception('Input is not batch sized')
             self.blobs[in_].data[...] = blob
 
     self._forward()
@@ -91,10 +91,10 @@ def _Net_backward(self, diffs=None, **kwargs):
         # Set top diffs according to defined shapes and make arrays single and
         # C-contiguous as Caffe expects.
         for top, diff in kwargs.iteritems():
-            if diff.shape[0] != self.blobs[top].num:
-                raise Exception('Diff is not batch sized')
             if diff.ndim != 4:
                 raise Exception('{} diff is not 4-d'.format(top))
+            if diff.shape[0] != self.blobs[top].num:
+                raise Exception('Diff is not batch sized')
             self.blobs[top].diff[...] = diff
 
     self._backward()