Forbidden Control Character Error for imaginary element

[skuschel]

I believe that 397cc98 introduced a bug or at least it changed the behavior:

I used to do something like this, of course with x being a large array:

import numexpr as ne
x = 5
y = ne.evaluate('exp(1.j*x)')

As of the mentioned change, this gives me an "Expression has forbidden control character" error.
It works with ints e.g 'exp(1j*x)', but 'exp(1.5j*x)' is also raising the error.

[FrancescAlted]

Fixed by #462