Enable experimental Docker features in CircleCI

Author: deliahu

.circleci/config.yml

@@ -116,7 +116,7 @@ jobs:
     docker:
       - image: circleci/python:3.6
     environment:
-      NUM_BUILD_PROCS: "2"
+      DOCKER_CLI_EXPERIMENTAL: enabled
     steps:
       - checkout
       - setup_remote_docker:
@@ -141,6 +141,7 @@ jobs:
       - image: circleci/python:3.6
     environment:
       CORTEX_TEST_BATCH_S3_PATH: s3://cortex-nightly-artifacts/test/jobs
+      DOCKER_CLI_EXPERIMENTAL: enabled
     steps:
       - checkout
       - setup_remote_docker:

CONTRIBUTING.md

@@ -139,8 +139,6 @@ export DEFAULT_USER_ARN="arn:aws:iam::<ACCOUNT_ID>:<AWS IAM ENTITY>" # (e.g. arn
 # If you are working on govcloud, you will need to set credentials from a public (non govcloud) account to access inferentia ECR
 # export NORMAL_REGION_AWS_ACCESS_KEY_ID="***"
 # export NORMAL_REGION_AWS_SECRET_ACCESS_KEY="***"
-
-# export NUM_BUILD_PROCS=2  # optional; can be >2 if you have enough memory
 ```
 
 Create the ECR registries: