Make sure that the float() input string is "ready" before parsing it.

Cython/Utility/Optimize.c

@@ -667,6 +667,8 @@ static CYTHON_INLINE double __Pyx_PyUnicode_AsDouble(PyObject *obj) {
     // Currently not optimised for 1) Py2.7 and 2) Py3 unicode strings with non-ASCII whitespace.
     // See __Pyx__PyBytes_AsDouble() below, the same byte buffer copying could be done here.
 #if PY_MAJOR_VERSION >= 3
+    if (unlikely(PyUnicode_READY(obj) == -1))
+        return (double)-1;
     if (likely(PyUnicode_IS_ASCII(obj))) {
         const char *s;
         Py_ssize_t length;