chore: show-spring-boot-version-diff.sh now fails when Spring's POM url not found

Author: php-coder

src/main/scripts/show-spring-boot-version-diff.sh

@@ -18,15 +18,15 @@ SPRING_VERSION='2.2.13.RELEASE'
 #SPRING_VERSION="$(grep -FA1 '<artifactId>spring-boot-starter-parent' "$PROJECT_POM" | awk -F'[<>]' '/<version>/{print $3}')"
 
 # @todo #869 show-spring-boot-version-diff.sh: properly handle recursive properties
-SPRING_POM="https://raw.githubusercontent.com/spring-projects/spring-boot/v$SPRING_VERSION/spring-boot-project/spring-boot-dependencies/pom.xml"
+SPRING_POM="$(curl -sS --fail-with-body https://raw.githubusercontent.com/spring-projects/spring-boot/v$SPRING_VERSION/spring-boot-project/spring-boot-dependencies/pom.xml)"
 
 printf "Comparing with Spring Boot %s (project vs spring versions)\\n\\n" "$SPRING_VERSION"
 
 # I know about useless cat below, but it's here for better readability.
 # shellcheck disable=SC2002
 join \
-	<(cat    "$PROJECT_POM" | awk -F'[<>]' -v OFS='\t' '$2~/\.version$/{print $2, $3}' | sort) \
-	<(curl -sS --fail-with-body "$SPRING_POM" | awk -F'[<>]' -v OFS='\t' '$2~/\.version$/{print $2, $3}' | sort) \
+	<(cat "$PROJECT_POM" | awk -F'[<>]' -v OFS='\t' '$2~/\.version$/{print $2, $3}' | sort) \
+	<(echo "$SPRING_POM" | awk -F'[<>]' -v OFS='\t' '$2~/\.version$/{print $2, $3}' | sort) \
 	| awk '
 			{
 				if ($2 != $3){