Fixed error handling when status code is not 200.
Fixed error handling when status code is not 200.

Signed-off-by: Kouhei Maeda <c9f1823971fa1a4c79cdb50b3311094021cee31e@palmtb.net>

bountylabs/http-digest-auth-client,ryanjdew/http-digest-auth-client,pteich/http-digest-auth-client