fix: Substantially improve error messages if the pact publisher API fails

Author: TimothyJones

src/publisher.ts

@@ -111,9 +111,15 @@ export class Publisher {
         instance.once('close', (code) => {
           const o = output.join('\n');
           const pactUrls = /https?:\/\/.*\/pacts\/.*$/gim.exec(o);
-          if (code !== 0 || !pactUrls) {
-            logger.error(`Could not publish pact:\n${o}`);
-            return reject(new Error(o));
+          if (code !== 0) {
+            const message = `Pact publication failed with non-zero exit code. Full output was:\n${o}`;
+            logger.error(message);
+            return reject(new Error(message));
+          }
+          if (!pactUrls) {
+            const message = `Publication appeared to fail, as we did not detect any pact URLs in the following output:\n${o}`;
+            logger.error(message);
+            return reject(new Error(message));
           }
 
           logger.info(o);