diff --git a/lib/asyncMainWrap.js b/lib/asyncMainWrap.js
index <HASH>..<HASH> 100644
--- a/lib/asyncMainWrap.js
+++ b/lib/asyncMainWrap.js
@@ -1,8 +1,10 @@
 function exitWithError(err) {
-  if (!process.env.DEBUG && err.customOutput) {
+  if (process.env.DEBUG) {
+    console.error(err);
+  } else if (err.customOutput) {
     console.error(err.customOutput);
   } else {
-    console.error(err);
+    console.error(err.stack);
   }
 
   if (typeof err.exitCode === "number") {
Only print err.stack by default [BREAKING]

Since introducing the processError option and the
customOutput property on error objects we can drop
the verbosity from the default output.

Instead of logging the err object itself, we now just
print the contents of `err.stack`.

Setting the DEBUG environment variable will trigger the
old behavior still, as well as disable any custom output.