Add error message to build description

Change-Id: Ifffce007fbe9d3bc47ea57c30ee652b5e0bdb680
diff --git a/git-merge-branches-pipeline.groovy b/git-merge-branches-pipeline.groovy
index cff1db5..0d8c47b 100644
--- a/git-merge-branches-pipeline.groovy
+++ b/git-merge-branches-pipeline.groovy
@@ -22,6 +22,7 @@
   } catch (Throwable e) {
      // If there was an error or exception thrown, the build failed
      currentBuild.result = "FAILURE"
+     currentBuild.description = e.message
      throw e
   }
 }