put compiling message only after checking for binary

lib/modules/vyper/index.js

@@ -35,7 +35,6 @@ class Vyper {
     if (!contractFiles || !contractFiles.length) {
       return cb();
     }
-    self.logger.info(__("compiling Vyper contracts") + "...");
 
     const vyper = shelljs.which('vyper');
     if (!vyper) {
@@ -43,6 +42,7 @@ class Vyper {
       self.logger.info(__('You can install it by visiting: %s', 'https://vyper.readthedocs.io/en/latest/installing-vyper.html'));
       return cb();
     }
+    self.logger.info(__("compiling Vyper contracts") + "...");
 
     const compiled_object = {};
     async.each(contractFiles,