# error when perform symbolic calculation in Octave of Sage

I have tried the Octave (matlab-like) kernel in Sagemathcloud, but when I intended to perform the symbolic calculation in Octave, something strange happened, and I can't solve it.

My code is as follows:

```
pkg load symbolic
syms x
f = sin(x)^2;
diff(f)
```

when I execute it, error happened, it said

'ascii' codec can't encode character u'\u22c5' in position 13: ordinal not in range(128)

How can I solve this problem?