closes serverless#194

- skip requirement generation, if no requirements file is present

Author: bweigel

lib/pip.js

@@ -385,6 +385,11 @@ function installRequirementsIfNeeded(
   // Our source requirements, under our service path, and our module path (if specified)
   const fileName = path.join(servicePath, modulePath, options.fileName);
 
+  // Skip requirements generation, if requirements file doesn't exist
+  if (!fse.existsSync(fileName)) {
+    return false;
+  }
+
   let requirementsTxtDirectory;
   // Copy our requirements to another filename in .serverless (incase of individually packaged)
   if (modulePath && modulePath != '.') {