Check the output status of gogenerate.sh

This is because it may fail if the codegen tools are not found.

If failed, skip the status compare step because it may as well return a
false positive, i.e. generated code is not up to date but the codegen
tool to bring it up to date was not found so no diff was detected.

scripts/travis_checker.sh

@@ -52,16 +52,25 @@ echo "Running go generate..."
 gogenerate_status_before="${tmpdir}/gogenerate_status_before.txt"
 gogenerate_status_after="${tmpdir}/gogenerate_status_after.txt"
 gogenerate_status_diff="${tmpdir}/gogenerate_status.diff"
+gogenerate_output="${tmpdir}/gogenerate_output.txt"
 git status --porcelain=v2 > "${gogenerate_status_before}"
-"${progdir}/gogenerate.sh"
-git status --porcelain=v2 > "${gogenerate_status_after}"
-if diff -u "${gogenerate_status_before}" "${gogenerate_status_after}" \
-	> "${gogenerate_status_diff}"
+if "${progdir}/gogenerate.sh" > "${gogenerate_output}" 2>&1
 then
-	echo "go generate succeeded; all generated files seem up to date."
+	echo "go generate succeeded."
+	echo "Checking if go generate changed any files..."
+	git status --porcelain=v2 > "${gogenerate_status_after}"
+	if diff -u "${gogenerate_status_before}" "${gogenerate_status_after}" \
+		> "${gogenerate_status_diff}"
+	then
+		echo "All generated files seem up to date."
+	else
+		echo "go generate changed working tree contents!"
+		"${progdir}/print_file.sh" "${gogenerate_status_diff}" "git status diff"
+		ok=false
+	fi
 else
-	echo "go generate changed working tree contents!"
-	"${progdir}/print_file.sh" "${gogenerate_status_diff}" "git status diff"
+	echo "go generate FAILED!"
+	"${progdir}/print_file.sh" "${gogenerate_output}" "go generate"
 	ok=false
 fi