release_upgrade: move set trap to a common place

bin/epm-release_upgrade

@@ -308,8 +308,7 @@ __switch_alt_to_distro()
 	local FROM="$1"
 	info
 
-	__save_alt_repo_lists
-	trap __restore_alt_repo_lists EXIT
+	try_change_alt_repo
 
 	case "$*" in
 		"p6"|"p6 p7"|"t6 p7"|"c6 c7")
@@ -458,12 +457,12 @@ __switch_alt_to_distro()
 			else
 				warning "Unknown distro version. Have no idea how to switch from $DISTRNAME $FROM to $DISTRNAME $TO."
 			fi
-			trap - EXIT
+			end_change_alt_repo
 			info "Try run f.i. '# epm release-upgrade p10' or '# epm release-downgrade p9' or '# epm release-upgrade Sisyphus'"
 			info "Also possible you need install altlinux-release-p? package for correct distro version detecting"
 			return 1
 	esac
-	trap - EXIT
+	end_change_alt_repo
 	epm clean
 	info "Note: Also you can try '# epm autoremove' and '# epm autoorphans' commands to remove obsoleted and unused packages."
 }

bin/epm-reposave

@@ -52,6 +52,16 @@ __restore_alt_repo_lists()
 	done
 }
 
+try_change_alt_repo()
+{
+	__save_alt_repo_lists
+	trap __restore_alt_repo_lists EXIT
+}
+
+end_change_alt_repo()
+{
+	trap - EXIT
+}
 
 
 epm_reposave()

bin/epm-upgrade

@@ -43,7 +43,7 @@ epm_upgrade()
 			# install only installed packages (simulate upgrade packages)
 			installlist="$(get_only_installed_packages "$installlist")"
 			[ -n "$verbose" ] && info "Packages to upgrade: $installlist"
-			(pkg_names="$installlist" epm_Install)
+			(pkg_names="$installlist" epm_Install) || fatal "Can't update repo"
 			epm_removerepo "$@"
 			return
 		fi