tests: Authenticate to AWS Elastic Container Registry for docker pull

This should increase the rate limit from 1/s to 10/s. AWS
credentials are obtained from environment variables in Azure
pipelines, or the default AWS CLI profile.

https://docs.aws.amazon.com/AmazonECR/latest/public/public-service-quotas.html
https://docs.aws.amazon.com/AmazonECR/latest/public/public-registries.html#public-registry-auth
https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-envvars.html
(cherry picked from commit 0db7467)

Author: moreati

.ci/ansible_install.py

@@ -12,12 +12,15 @@
             '-r tests/requirements.txt '
             '-r tests/ansible/requirements.txt',
         'pip install -q ansible=={0}'.format(ci_lib.ANSIBLE_VERSION)
+    ],
+    [
+        'aws ecr-public get-login-password | docker login --username AWS --password-stdin public.ecr.aws',
     ]
 ]
 
-batches.append(ci_lib.throttle(
+batches[-1].extend([
     'docker pull %s' % (ci_lib.image_for_distro(distro),)
     for distro in ci_lib.DISTROS
-))
+])
 
 ci_lib.run_batches(batches)

.ci/azure-pipelines-steps.yml

@@ -39,6 +39,10 @@ steps:
 
 - script: .ci/$(MODE)_install.py
   displayName: "Run $(MODE)_install.py"
+  env:
+    AWS_ACCESS_KEY_ID: $(AWS_ACCESS_KEY_ID)
+    AWS_SECRET_ACCESS_KEY: $(AWS_SECRET_ACCESS_KEY)
+    AWS_DEFAULT_REGION: $(AWS_DEFAULT_REGION)
 
 - script: .ci/$(MODE)_tests.py
   displayName: "Run $(MODE)_tests.py"

.ci/debops_common_install.py

@@ -13,6 +13,7 @@
         'pip install -qqqU debops==0.7.2 ansible==%s' % ci_lib.ANSIBLE_VERSION,
     ],
     [
+        'aws ecr-public get-login-password | docker login --username AWS --password-stdin public.ecr.aws',
         'docker pull %s' % (ci_lib.image_for_distro('debian'),),
     ],
 ])

.ci/mitogen_install.py

@@ -11,6 +11,7 @@
 
 if ci_lib.have_docker():
     batches.append([
+        'aws ecr-public get-login-password | docker login --username AWS --password-stdin public.ecr.aws',
         'docker pull %s' % (ci_lib.image_for_distro(ci_lib.DISTRO),),
     ])
 

.ci/mitogen_py24_install.py

@@ -4,6 +4,7 @@
 
 batches = [
     [
+        'aws ecr-public get-login-password | docker login --username AWS --password-stdin public.ecr.aws',
         'docker pull %s' % (ci_lib.image_for_distro(ci_lib.DISTRO),),
     ],
     [