default the compatible runtimes to the provider runtime. (If its undefined, serverless core will remove it when creating the layer.)

Author: david-mkl

lib/layer.js

@@ -57,7 +57,8 @@ function createLayers() {
   this.serverless.service.layers['pythonRequirements'] = Object.assign({
       artifact: path.join('.serverless', 'pythonRequirements.zip'),
       name: `${this.serverless.service.stage}-python-requirements`,
-      description: 'Python requirements generated by serverless-python-requirements.'
+      description: 'Python requirements generated by serverless-python-requirements.',
+      compatibleRuntimes: [this.serverless.service.provider.runtime],
     },
     this.options.layer
   );