BLD: fix cython error on master-branch cython

Cython now complains if the types of the two branches in the ternary
statement do not match (here 1D vs 2D).

scipy/spatial/transform/rotation.py

@@ -861,7 +861,11 @@ def from_euler(cls, seq, angles, degrees=False):
                              "num_axes), got {}.".format(angles.shape))
 
         quat = _elementary_quat_compose(seq, angles, intrinsic)
-        return cls(quat[0] if is_single else quat, normalize=False, copy=False)
+
+        if is_single:
+            return cls(quat[0], normalize=False, copy=False)
+        else:
+            return cls(quat, normalize=False, copy=False)
 
     def as_quat(self):
         """Represent as quaternions.