Handle errors during read in updateFile()
Handle errors during read in updateFile()

Closes: #774
Approved by: j-mracek

hughsie/libhif,rpm-software-management/libhif,hughsie/libhif,rpm-software-management/libhif,rpm-software-management/libdnf,rpm-software-management/libdnf,hughsie/libhif,rpm-software-management/libdnf,hughsie/libhif,rpm-software-management/libdnf,rpm-software-management/libhif,rpm-software-management/libhif