Help pepole debug when mvn build fails

src/bin/keycloakify/buildJars/buildJar.ts

@@ -220,13 +220,17 @@ export async function buildJar(params: {
         );
     }
 
+    {
+        const mvnBuildCmd = `mvn clean install -Dmaven.repo.local="${pathJoin(keycloakifyBuildCacheDirPath, ".m2")}"`;
+
         await new Promise<void>((resolve, reject) =>
             child_process.exec(
-            `mvn clean install -Dmaven.repo.local="${pathJoin(keycloakifyBuildCacheDirPath, ".m2")}"`,
+                mvnBuildCmd,
                 { cwd: keycloakifyBuildCacheDirPath },
                 error => {
                     if (error !== null) {
                         console.error(
+                            [
                                 `Build jar failed: ${JSON.stringify(
                                     {
                                         jarFileBasename,
@@ -235,7 +239,10 @@ export async function buildJar(params: {
                                     },
                                     null,
                                     2
-                        )}`
+                                )}`,
+                                "Try running the following command to debug the issue (you are probably under a restricted network and you need to configure your proxy):",
+                                `cd ${keycloakifyBuildCacheDirPath} && ${mvnBuildCmd}`
+                            ].join("\n")
                         );
 
                         reject(error);
@@ -245,6 +252,7 @@ export async function buildJar(params: {
                 }
             )
         );
+    }
 
     await fs.rename(
         pathJoin(