Removing a column that is not in the columnset is error

```
import datatable as dt
from datatable import f
#
#print(dt.__version__)
# '1.0.0'
df1 = dt.Frame({'a':[1, 2, 3], 'b':[2, 3, 4],'c':[1., 2., 3.]})
df1[:, f[:].remove(f['d'])]
#
# KeyError: Column d does not exist in the Frame; did you mean a, b or c?
```