Merge pull request #159 from batmat/more-diagnostics-when-no-url-vali…

…dity

Chain the cause exception and log in case of failure

src/main/java/org/jenkinsci/plugins/github_branch_source/GitHubSCMSource.java

@@ -1291,7 +1291,7 @@ private void checkApiUrlValidity(GitHub github) throws IOException {
             github.checkApiUrlValidity();
         } catch (HttpException e) {
             String message = String.format("It seems %s is unreachable", apiUri == null ? GITHUB_URL : apiUri);
-            throw new AbortException(message);
+            throw new IOException(message, e);
         }
     }