doc: clarify tutorial error section
doc: clarify tutorial error section

Signed-off-by: Davide "FunkyAss" Del Zompo <c04902a01a5473de14074df67901f06c72295496@gmail.com>
Reviewed-by: Andreas Schneider <5be00ddc76278cf6077f5047ca3384a88460c671@cryptomilk.org>

wangshawn/libssh,robxu9/libssh,mwgoldsmith/libssh,DouglasHeriot/libssh,kedazo/libssh,taikoo/libssh,DouglasHeriot/libssh,robxu9/libssh,kedazo/libssh,robxu9/libssh,robxu9/libssh,nviennot/libssh,mwgoldsmith/ssh,kedazo/libssh,Distrotech/libssh,pouete/libssh,nviennot/libssh,sebadoom/libssh,Distrotech/libssh,mwgoldsmith/libssh,sebadoom/libssh,DouglasHeriot/libssh,pouete/libssh,sebadoom/libssh,nviennot/libssh,nviennot/libssh,DouglasHeriot/libssh,sebadoom/libssh,kedazo/libssh,pouete/libssh,wangshawn/libssh,taikoo/libssh,Distrotech/libssh,wangshawn/libssh,wangshawn/libssh,pouete/libssh,mwgoldsmith/libssh,Distrotech/libssh,taikoo/libssh,mwgoldsmith/ssh,mwgoldsmith/ssh,taikoo/libssh,mwgoldsmith/libssh,mwgoldsmith/ssh