fix: Catch and ignore pretty-error errors

Fixes #921

lib/errors.js

@@ -18,7 +18,14 @@ module.exports = function (err, context) {
       return JSON.stringify(this.toHtml());
     },
     toString: function () {
-      return prettyError.render(err).replace(/webpack:\/\/\/\./g, context);
+      try {
+        return prettyError.render(err).replace(/webpack:\/\/\/\./g, context);
+      } catch (e) {
+        // This can sometimes fail. We don't know why, but returning the
+        // original error is better than returning the error thrown by
+        // pretty-error.
+        return err;
+      }
     }
   };
 };