Add virtualenv option to Python examples (pulumi#885)

Use the automatically managed `virtualenv: venv` support in all Python examples.

See https://www.pulumi.com/docs/intro/languages/python/#virtual-environments.

Also update the READMEs to no longer mention needing to manually create the virtual environment. The Pulumi CLI, as of v2.15.1, will automatically create & install dependencies in a virtual environment if the `virtualenv` runtime option is set in `Pulumi.yaml` and the configured directory is empty or doesn't exist.

Author: Luke Hoban

aws-django-voting-app/Pulumi.yaml

@@ -1,5 +1,8 @@
 name: voting-app
-runtime: python
+runtime:
+  name: python
+  options:
+    virtualenv: venv
 description: Voting app that uses containers
 template:
   config:

aws-django-voting-app/README.md

@@ -39,16 +39,6 @@ The example shows how easy it is to deploy containers into production and to con
     $ pulumi config set django-secret-key <VALUE> --secret
     ```
 
-1. Create a Python virtualenv, activate it, and install dependencies:
- 
-    This installs the dependent packages [needed](https://www.pulumi.com/docs/intro/concepts/how-pulumi-works/) for our Pulumi program.
-
-    ```bash
-    $ python3 -m venv venv
-    $ source venv/bin/activate
-    $ pip3 install -r requirements.txt
-    ```
-
 1. Run `pulumi up -y` to deploy changes:
 
     ```bash

aws-py-appsync/Pulumi.yaml

@@ -1,5 +1,8 @@
 name: aws-py-appsync
-runtime: python
+runtime:
+  name: python
+  options:
+    virtualenv: venv
 description: Basic example of defining an AWS AppSync endpoint from Pulumi in Python
 template:
   config:

aws-py-appsync/README.md

@@ -18,17 +18,6 @@ This example shows how to setup a basic GraphQL endpoint in AWS AppSync. The end
     $ pulumi config set aws:region us-east-2
     ```
 
-1. Create a Python virtualenv, activate it, and install dependencies:
-
-    This installs the dependent packages [needed](https://www.pulumi.com/docs/intro/concepts/how-pulumi-works/) for our Pulumi program.
-
-
-    ```bash
-    $ python3 -m venv venv
-    $ source venv/bin/activate
-    $ pip3 install -r requirements.txt
-    ```
-
 1. Run `pulumi up` to preview and deploy changes:
 
     ```bash

aws-py-assume-role/README.md

@@ -23,19 +23,10 @@ resources.
 You'll need to set the `create-role:unprivilegedUsername` configuration variable to the name of the unprivilged user, as
 well as the AWS region in which to operate.
 
-First, you need install dependencies. In this example we will install them in
-a virtual environment named `venv`.
+First, you need to create a new stack:
 
 ```bash
 $ cd create-role
-$ python3 -m venv venv
-$ source venv/bin/activate
-$ pip install -r requirements.txt
-```
-
-Now create a new stack: 
-
-```bash
 $ pulumi stack init assume-role-create
 $ pulumi config set create-role:unprivilegedUsername somebody@pulumi.com
 $ pulumi config set aws:region us-east-1
@@ -70,8 +61,7 @@ with the unprivileged user credentials created in Part 1. This can be configured
 directory, replacing `{YOUR_STACK_PATH/assume-role-create}` with the full name of your stack from Part 1. Full name of your stack is available at [`app.pulumi.com`][app]
 
 ```bash
-$ cd assume-role
-$ npm install
+$ cd ../assume-role
 $ export AWS_ACCESS_KEY_ID="$(pulumi stack output --stack {YOUR_STACK_PATH/assume-role-create} accessKeyId)"
 $ export AWS_SECRET_ACCESS_KEY="$(pulumi stack output --stack {YOUR_STACK_PATH/assume-role-create} --show-secrets secretAccessKey)"
 ```

aws-py-assume-role/assume-role/Pulumi.yaml

@@ -1,3 +1,6 @@
 name: assume-role
-runtime: python
+runtime:
+  name: python
+  options:
+    virtualenv: venv
 description: Demonstrate use of AWS AssumeRole Functionality

aws-py-assume-role/create-role/Pulumi.yaml

@@ -1,3 +1,6 @@
 name: create-role
-runtime: python
+runtime:
+  name: python
+  options:
+    virtualenv: venv
 description: Demonstrate use of AWS AssumeRole Functionality

aws-py-dynamicresource/README.md

@@ -28,16 +28,6 @@ A simple example demonstrating how to write Dynamic Providers using Pulumi.
     $ pulumi config set sql-user-password <PASSWORD> --secret
     ```
 
-1. Create a Python virtualenv, activate it, and install dependencies:
-
-    This installs the dependent packages [needed](https://www.pulumi.com/docs/intro/concepts/how-pulumi-works/) for our Pulumi program.
-
-    ```bash
-    $ python3 -m venv venv
-    $ source venv/bin/activate
-    $ pip3 install -r requirements.txt
-    ```
-
 1. Run `pulumi up -y` to deploy changes:
 
     ```bash

aws-py-ec2-provisioners/Pulumi.yaml

@@ -1,3 +1,6 @@
 name: aws-py-ec2-provisioners
-runtime: python
+runtime:
+  name: python
+  options:
+    virtualenv: venv
 description: An example of manually configuring an AWS EC2 virtual machine

aws-py-ec2-provisioners/README.md

@@ -10,14 +10,6 @@ https://github.com/pulumi/pulumi/issues/1691 tracks designing and developing a c
 
 First, create a stack, using `pulumi stack init`.
 
-Now, we need to ensure that our dependencies are installed:
-
-```
-$ python3 -m venv venv
-$ source venv/bin/activate
-$ pip3 install -r requirements.txt
-```
-
 Next, generate an OpenSSH keypair for use with your server - as per the AWS [Requirements][1]
 
 ```