Vendor python dependencies

Author: peter-evans

.gitignore

@@ -1,3 +1,6 @@
 __pycache__
+.python-version
+
 node_modules
+
 .DS_Store

dist/index.js

@@ -1018,7 +1018,9 @@ async function run() {
     await exec.exec("pip", [
       "install",
       "--requirement",
-      `${src}/requirements.txt`
+      `${src}/requirements.txt`,
+      "--no-index",
+      `--find-links=${__dirname}/vendor`
     ]);
 
     // Fetch action inputs