No longer rely on system Python for installs of python3 runtime

README.md

@@ -80,7 +80,7 @@ implemented are:
  * `nodejs14.x` for Node.js Lambda functions using a downloaded Node v14.18.1 binary
  * `python` for Python Lambda functions using the system `python` binary
  * `python2.7` for Python Lambda functions using a downloaded Python v2.7.12 binary
- * `python3` for Python Lambda functions using the system `python3` binary (or fallback to `python`)
+ * `python3` for Python Lambda functions using the system `python3` binary
  * `python3.6` for Python Lambda functions using a downloaded Python v3.6.8 binary
  * `python3.7` for Python Lambda functions using a downloaded Python v3.7.2 binary
  * `go1.x` for Lambda functions written in Go - binary must be compiled for your platform

src/runtimes/python3/index.ts

@@ -1,6 +1,10 @@
 import { Runtime } from '../../types';
+import { installPython } from '../../install-python';
 import { runtimes, initializeRuntime } from '../../runtimes';
 
-export async function init(_runtime: Runtime): Promise<void> {
-	await initializeRuntime(runtimes.python);
+export async function init({ cacheDir }: Runtime): Promise<void> {
+	await Promise.all([
+		initializeRuntime(runtimes.python),
+		installPython(cacheDir, '3.6.8')
+	]);
 }

test/test.ts

@@ -719,7 +719,7 @@ it(
 			}),
 		async fn => {
 			const payload = await fn();
-			assert.equal(payload['platform.python_version'][0], '3');
+			assert.equal(payload['platform.python_version'], '3.6.8');
 		}
 	)
 );