fix(lambda-python): install rsync if necessary

packages/@aws-cdk/aws-lambda-python/lib/Dockerfile

@@ -0,0 +1,9 @@
+# The correct AWS SAM build image based on the runtime of the function will be
+# passed as build arg. The default allows to do `docker build .` when testing.
+ARG IMAGE=amazon/aws-sam-cli-build-image-python3.7
+FROM $IMAGE
+
+# Ensure rsync is installed
+RUN yum -q list installed rsync &>/dev/null || yum install -y rsync
+
+CMD [ "python" ]

packages/@aws-cdk/aws-lambda-python/lib/bundling.ts

@@ -22,18 +22,25 @@ export interface BundlingOptions {
  * Produce bundled Lambda asset code
  */
 export function bundle(options: BundlingOptions): lambda.AssetCode {
+  // Bundling image derived from runtime bundling image (AWS SAM docker image)
+  const image = cdk.BundlingDockerImage.fromAsset(__dirname, {
+    buildArgs: {
+      IMAGE: options.runtime.bundlingDockerImage.image,
+    },
+  });
+
   let installer = options.runtime === lambda.Runtime.PYTHON_2_7 ? Installer.PIP : Installer.PIP3;
 
   let hasRequirements = fs.existsSync(path.join(options.entry, 'requirements.txt'));
 
   let depsCommand = chain([
     hasRequirements ? `${installer} install -r requirements.txt -t ${cdk.AssetStaging.BUNDLING_OUTPUT_DIR}` : '',
-    `cp -au . ${cdk.AssetStaging.BUNDLING_OUTPUT_DIR}`,
+    `rsync -r . ${cdk.AssetStaging.BUNDLING_OUTPUT_DIR}`,
   ]);
 
   return lambda.Code.fromAsset(options.entry, {
     bundling: {
-      image: options.runtime.bundlingDockerImage,
+      image,
       command: ['bash', '-c', depsCommand],
     },
   });

packages/@aws-cdk/aws-lambda-python/test/bundling.test.ts

@@ -21,7 +21,7 @@ test('Bundling', () => {
     bundling: expect.objectContaining({
       command: [
         'bash', '-c',
-        'cp -au . /asset-output',
+        'rsync -r . /asset-output',
       ],
     }),
   });
@@ -48,7 +48,7 @@ test('Bundling with requirements.txt installed', () => {
     bundling: expect.objectContaining({
       command: [
         'bash', '-c',
-        'pip3 install -r requirements.txt -t /asset-output && cp -au . /asset-output',
+        'pip3 install -r requirements.txt -t /asset-output && rsync -r . /asset-output',
       ],
     }),
   });
@@ -72,7 +72,7 @@ test('Bundling Python 2.7 with requirements.txt installed', () => {
     bundling: expect.objectContaining({
       command: [
         'bash', '-c',
-        'pip install -r requirements.txt -t /asset-output && cp -au . /asset-output',
+        'pip install -r requirements.txt -t /asset-output && rsync -r . /asset-output',
       ],
     }),
   });