Before a error handler was installed by init_pygsl into gsl which translated
the error code (and the message) to a python exception.
This required that the GIL was available, which numpy ufuncs dispose. Thus
now this gsl error handler is deactivated and instead the C error code
returned by the C function is translated to an error code by the wrapper
called from python.
UFuncs do not call this handler now at all.